Acute Presentation of Muscle Weakness

Author: Thomas J. Abrunzo, MD, MS, MPH, FACEP, FAAP, Co-Director, After Hours Pediatrics, Inc., Tampa, FL.

Peer Reviewer: Mary Jo Bowman, MD, Assistant Professor of Clinical Pediatrics, Ohio State University College of Medicine; Attending Physician, Pediatric Emergency Medicine, Children’s Hospital, Columbus, OH.

The assessment, evaluation, and management of a child with a complaint of weakness is a tremendous challenge to the emergency physician. Not only must one achieve an understanding of the parental concern, but a directed diagnostic evaluation must be formulated. The author does an excellent job of taking a very difficult issue and targeting pertinent historical and physical findings to direct the physician to an appropriate differential diagnosis. The glossary following the article provides useful information for formulating a differential and examining the child with a known disease process.

—The Editor

Definition of the Problem

The evaluation and treatment of acute weakness can be a daunting challenge to the skills of the emergency physician (EP). The pediatric patient expands this challenge. The practitioner’s goal in meeting this challenge is fourfold:

1. Achieving effective communication with a child and his or her parents;
2. Appreciating developmental variation in childhood;
3. Generating a pediatric differential diagnosis; and
4. Administering appropriate child-dosed therapy.

Communicating with the pediatric patient-parent dyad is fraught with pitfalls. Parents, with the best of intentions, will perceive their child’s problem in their own range of experience. They may sometimes translate their perception into a misleading complaint. The EP is responsible for understanding a layperson’s perception of the child’s illness, judging the subjective information for its diagnostic value and utility, and translating it into a pediatric diagnostic framework. The same dynamic applies to information from the child historian.

The process of child development has implications for specific disease incidence, presentation, and course. This requires knowledge of common illnesses in childhood and familiarity with their presentation. Understanding the developmental phenomena of child behavior, motor milestones, and the evolution of reflexes is of particular importance in the clinical evaluation of weakness.

The third component of the challenge in diagnosing the cause of weakness is the vast range of systemic, neurological, and musculoskeletal problems that may present acutely. This challenge requires a general understanding of the physiology and pathophysiology of motor function and an awareness of all the possible pediatric etiologies.

A final challenge is treating weakness in the pediatric patient. The unique requirements in the emergency assessment and therapy of children are well-described in the pediatric advanced life-support courses. After emergency stabilization, optimal management of problems causing weakness depends on efficiently engaging the care of the primary care physician, with appropriate input from the pediatric subspecialist, whether he or she neurosurgeon, neurologist, orthopedist, immunologist, infectious disease specialist, or other consultant.

The chief complaint offered by a parent or a newly verbal child may require further careful solicitation and interpretation to enable the construction of an appropriate differential diagnosis. Depending on a child’s age and development and a parent’s or a child’s perception, weakness may have many different reference terms. (See Table 1.)

Table 1. Common Chief Complaints Referring to Weakness
Infant	Toddler	Child
weak tired sleepy lazy floppy "like a rag doll" poor feeding lethargic limp won’t crawl "can’t hold himself up" "just lays there" "just not himself" "the child is not right"	weak tired sleepy lazy clumsy listless won’t walk tripping crawling instead of walking "just not himself" "the child is not right" dizzy can’t climb stairs can’t get out of a chair	weak clumsy "just not himself" dizzy can’t keep up numb
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Weakness is defined as "lacking physical strength, energy, or vigor; feeble."¹ Practically, it means the inability to generate adequate power against resistance. Related terms include paresis, defined as slight or incomplete paralysis. Paralysis refers to loss or impairment of motor function due to a lesion of the neural or muscular mechanism. Palsy is another term for paralysis. Apraxia and dyspraxia are the inability or difficulty to perform complex, skilled movements in the presence of normal strength and coordination. Tone is the muscle’s intrinsic resistance to stretch. Hypotonia, while frequently occurring with weakness, is not the same as weakness. Deficits in cerebellar function can cause hypotonia with normal muscle strength. Similarly, children with cerebral palsy can demonstrate increased tone with muscles that are weak.

While weakness is objectively defined and quantified as a deficit in motor strength, there is certainly a subjective component of weakness that relates to mental status (i.e., a patient’s "energy or vigor"). The subjective component may, in fact, be the most compelling aspect of a patient’s illness. It may also be difficult for a parent to appreciate, and difficult for an EP to analyze, in the pre-verbal patient. The coincidence of mental status abnormalities and deficits in motor strength requires careful evaluation to determine if the mental status alteration is primary, secondary, or simply coincidental. This determination will help direct diagnostic efforts toward systemic or central nervous system disease, as opposed to a focus on a peripheral abnormality. Given the subjective nature of mental status evaluation in the pre-verbal child, the distinction of abnormal mental status is crucial to the diagnostic process. Mellick and Nass have described helpful, practical approaches to assessing mental status in the pediatric patient.^2,3

Clinical examples of primary mental status alteration accompanying weakness include depression, malingering, and conversion. Malaise, lassitude, and the absence of energy frequently accompany these illnesses as non-organic symptoms. Secondary mental status changes might be seen in infectious mononucleosis, for example, which does not usually involve an organic mental status component, yet physical disability may produce secondary mental status changes such as reactive depression. Coincidental mental status and physical symptoms may be seen with hypothyroidism, an illness with global organic effects, simultaneously compromising both the patient’s sense of well-being and energy and his or her physical ability to perform motor tasks.

Patient, parent, or examiner may misinterpret impaired motor function from pain, sensory loss, psychiatric disorders, rigidity, spasticity, or stiffness as muscle weakness. This phenomenon has been termed "pseudoweakness."

History and physical must fully characterize the problem as completely as possible to enable specification of cause and prescription of treatment. However, even with a careful, thorough evaluation, one may still have difficulty sorting out the primary cause of weakness in the urgent setting. Occult sedative ingestion represents a case in point, showing non-specific central nervous system (CNS) and peripheral neuromuscular abnormalities. Laboratory testing, radiographic and magnetic resonance imaging, and certain special studies may be needed to confirm the diagnosis. Sometimes only hospital admission with observation and serial examinations will allow an accurate diagnosis.

Etiology

The various diagnostic etiologies of weakness are noted in Table 2. These are grouped by anatomic area, by disease mechanism, or by the affected organ system. Accordingly, some entities appear in more than one category.

Table 2. Weakness: Differential Diagnosis
Neurologic	Cardiovascular	Musculoskeletal	Metabolic	Toxic	Endocrine
Stroke Guillain-Barré Myasthenia gravis Eaton-Lambert Transverse myelitis Trauma Disk disease Epidural abscess Spinal cord tumor Acute cerebellar ataxia Todd’s paralysis Polyneuritis	Hypotension/shock Dysrhythmias Hypoxemia Congestive heart failure Asthma and steriod therapy	Muscular dystrophy Myotonia Metabolic muscle disease Trauma Myositis Fracture Dislocation Subluxation Scurvy	Fever Hyperglycemia Hypoglycemia Hyperkalemia Hypokalemia Hypernatremia Hyponatremia Hypomagnesemia Periodic paralysis Hypercalcemia Hypocalcemia Porphyria Uremia	Sedative hypnotics Muscle relaxants Paralytics Organophosphates Heavy metals	Diabetes mellitus Hypothyroidism Hypoparathyroidism Pregnancy Pituitary insufficiency Hypoadrenalism
Traumatic	Inflammatory	Infectious	Psychosocial	Hematologic	Neoplastic
Head injury Vertebral fracture/dislocation Down syndrome Child abuse Dysbarism Hemophilia Post-injection neuropathy Disk disease	Guillain-Barré Polymyositis Dermatomyositis Transverse myelitis; Devic’s disease Rheumatoid arthritis	Botulism Tick paralysis Lyme disease Mycoplasma pneumoniae Campylobacter Poliomyelitis Epidural abscess Mononucleosis Diphtheria	Hysteria Conversion (Briquet’s syndrome) Somatization Hypochondriasis Factitious disorder Malingering Child abuse Munchausen Syndrome	Anemia Leukemia Hemophilia	Eaton-Lambert syndrome Leukemia Occult neuro- blastoma
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Pathophysiology

Once weakness is established as a problem, it may be analyzed regarding anatomic sites of origin: the brain (both psyche and motor centers); the spinal cord; and the periphery (nerves, neuromuscular junction and muscles). These sites are presented in Figure 1 in the left column. The middle column describes the corresponding physiology, and the right column notes some of the pathological processes responsible for acute weakness.

Clinical Features

The clinical evaluation of weakness is guided by the standard clinical paradigm: history, physical examination, and ancillary testing. The history should focus on a standard review of systems with particular attention to airway symptoms (difficulty breathing, swallowing) and past events that may be relevant to the current symptoms. The family should be questioned regarding new medications that may have precipitated the current symptoms. (See Table 3.) The historical clinical features are presented in Table 4. The parents should be questioned regarding the child’s general activity level and specific changes. The child’s ability to feed and the quantity of feeds should be noted. In a child younger than 3 months of age, poor feeding may be a significant indicator of underlying pathology. Although most children do not have a significant medical history, a child with known congenital heart disease or trauma may be at risk for complications. For example, a child with congenital heart disease may develop dysrthymias, and a child with a recent basilar skull fracture may develop meningitis.

Table 3. Drugs that May Exacerbate or Precipitate Myasthenia Gravis
Aggravate or Unmask	Induce
Streptomycin Propanolol Quinidine Chlorpromazine ACTH Thyroid hormones Tetracyclines Procainamide Lithium Phenytoin Corticosteroids	Gentamycin D-Penicillamine Trimethadone Neomycin Phenytoin Tetanus antitoxin
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Table 4. Weakness: Historical Clinical Features
History	Pertinence to Weakness
Chief Complaint
	See Table 1
Present Illness
	Function/part affected, severity, onset, site, progression, associated symptoms (pain, tenderness, fever)
Review of Systems
Skin	Rashes of specific infection or non-specific inflammation, ticks, pallor of anemia, diminished perfusion of shock, ecchymoses of hemophilia or abuse, pigmentation of hypoadrenalism
Lymph nodes	Infection with pseudoparalysis, tumors
Bones/joints/muscles	Fracture, subluxation with pseudoparalysis, back, neck pain
Hematopoietic	Anemia
Endocrine	Thyroid, parathyroid disease, diabetes
Allergic/immunologic	Autoimmune disease
Head	Trauma
Eyes	Diplopia, blurring, acuity changes from mass, trauma, hypoglycemia, electrolyte disorder, metabolic disease
Ears	Blood, CSF drainage from trauma; infection
Nose	Blood, CSF drainage from trauma; infection; URI symptoms
Mouth	Salivation from organophosphates
Throat	Airway or swallowing compromise from tumor, bleed, neuropathy/myopathy, diphtheritic pharyngitis
Neck	Meningismus of infection, bleed, trauma, disk disease
Breasts	Discharge, tumor, hypertrophy of endocrinopathy
Respiratory	Cyanosis, hypoxia, asthma, URI symptoms
Cardiovascular	CHF, dysrhythmia
Gastrointestinal	Vomiting, diarrhea with electrolyte imbalance
Genitourinary	Polyuria, dark urine of myoglobinuria
Nervous system	Stroke, trauma, tumor
Psychiatric	Malingering, hysteria, conversion
History
Birth Gestation Maternal Illnesses Weight Diet	Congenital illness, anomaly Perinatal insult; intracranial bleed, hypoxia, etc. Infections, autoimmune disease Prematurity, IUGR Unusual formula, preparation abnormalities, association of symptoms with meals in periodic paralysis
Surgery	Injuries, bleeding
Illnesses and injuries	Trauma to head, bone, joint, muscle
Hospitalizations	Related illnesses, treatments, medications
Social History
Behavior	Malingering, hysteria, conversion, somatization
Development	Delays in cognitive or motor function
Medications	Myopathic; neuropathic
Immunizations	Oral polio, measles, diphtheria
Diet	Vitamin C, B12 and Thiamine deficiency; B6 ingestion
Drugs	Sedative-hypnotics, heavy metals (lead, mercury, arsenic), organic solvents, cocaine, INH, pyridoxine, nitrofurantoin, vincristine
Illness exposure Pets Travel	Mononucleosis, Campylobacter, Polio, Mycoplasma Tick exposure Disease exposure
Family History
	Muscle, neurologic, autoimmune disease
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The developmental history of the child should be obtained to identify significant delays or developmental regression that usually indicates underlying pathology. (See Table 5.) Parents should also be queried regarding asymmetry, positioning, and preferential use of each extremity.

Table 5. Development Motor Milestones⁶
Age	Milestones
4 mos 5 mos 7-8 mos 9-10 mos 15 mos 2 yrs 2.5 yrs 3 yrs 4 yrs 5 yrs	Pulls to sit, good head control Rolls over Sits with support Stands with support Walks without support Climbs stairs Jumps with both feet Stands on one foot Hops Walks on straight line; balances on one foot
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The paramount goal of the EP is to diagnose and treat pre-arrest conditions. Initial evaluation is, therefore, directed to this urgency. Neuromuscular dysfunction can unpredictably compromise respiratory function. The medical caretaker must be constantly vigilant of this possibility. The younger the child, the greater the possibility that the chief complaint of weakness may represent such impending catastrophes as septic shock, congestive heart failure, increased intracranial pressure, or status epilepticus. These very serious problems can present with deceptively subtle symptoms in the pre-verbal child. The child’s general appearance is usually most revealing: alertness, responsiveness, and consolability reflect well-being. Irritability, lethargy, and inconsolability are worrisome for serious illness. A malnourished child should lead one to suspect a chronic illness (cardiac, GI) or parental neglect. The physician should observe the general strength of the child, ability to hold head upright, and movement of all four extremities.

Methodical attention to vital sign normality and vital sign stability gives further evidence of a child’s well-being. Vital sign abnormality and/or instability are concerns for significant illness. Bradycardia is particularly concerning for CNS disease, whereas tachycardia may lead the physician to suspect sepsis or ingestion. A complete physical exam with special attention to muscle strength, reflexes, and presence or absence of pediatric reflexes should be conducted. Table 6 presents typical abnormalities that on physical examination will direct suspicion to a specific diagnosis. The head should be examined for evidence of trauma and the fontanelle assessed. A bulging fontanelle suggests increased intracranial pressure. If it is associated with widening of the suture spaces, it would suggest a chronic process (tumor, hydrocephalus). If the sutures are not "split," it suggests an acute process such as meningitis or trauma. The child’s cry should also be noted. A high-pitched cry may be associated with CNS disease. The child’s general muscle mass and tone should be noted. Atrophy or hypertrophy of muscle groups should be identified.

Table 6. Weakness: Physical Examination Clinical Features
Physical Examination	Pertinence to Weakness
Vital Signs
Temperature Pulse Heart rate Blood pressure Weight	Infection, inflammation Infection, inflammation Infection, inflammation Sepsis, spinal injury Malnutrition, acute fluid loss/gain
General Appearance
Facies Comfort/distress Alertness Quality of cry Consolable Activity Responsiveness Nutritional status HEENT	Cushingoid Pain, tenderness Alteration with CNS depression Hi-pitched with CNS disease Inconsolable with CNS disease Guarded secondary to pain Discomfort Calorie or vitamin deficiency Tauma, fundi, fontanelle, extraocular muscles, pupillary reaction/equality, blood/CSF in ear canals/nares, lacrimation, salivation with organophosphates
Chest Heart Abdomen Skin Genitalia Extremities and spine	Dyspnea, tachypnea, distress for hypoxia, wheezing Arrhythmia, tachycardia, gallop, murmur Liver, spleen, tumor Rash, tick, ecchymoses, inflammation, striae, pigmentation Bulk, atrophy, hypertrophy, tone, contracture, back pain, neck pain, extremity pain, dislocation
Neurologic Mental status Cranial nerves Motor Sensory Reflexes Gait Cerebellar	Orientation, alertness, responsiveness, cognition C.N. II, III, IV, VI, VII, VIII, IX, XII Rigidity, flaccidity, spasm, paralysis, strength,* movement, fasciculations, spasticity Pain, light, touch, vibration Babinski, clonus Ataxia, heel and toe gait Ataxia, nystagmus, Romberg, finger-to-nose, rapid alternating movements
* Quantitation of muscle function: The MRC system.⁷ 0 No movement evident 1 Trace of movement 2 Movement in horizontal plane but not against gravity 3 Moves against gravity but not against resistance 4 Moves against resistance but weak 5 Full strength against resistance ________________________________________________________________________________

The patient’s reflexes should then be assessed. Tables 7, 8, and 9 outline some of the motor reflexes unique to the developing child, and motor and reflex innervation. Table 7 also lists pathologic conditions that may be associated with an abnormality of the reflex.

Table 7. Tonic Neck Reflexes⁵
Evolution of Reflexes
Reflex	Appearance	Disappearance
Tonic neck reflex: Turning the head to one side causes ipsilateral extension of arm and leg, contralateral flexion of arm. Consistently asymmetrical response may be a sign of hemiparesis on the affected side.	2-3 wks	7-8 mos
Crossed adductor: Contraction of both hip adductors when either knee jerk is elicited. Persistence suggests pyramidal tract dysfunction.	2-3 mos	7-8 mos
Ankle clonus: Reflects upper motor neuron lesion. Represents pyramidal tract dysfunction.	Birth	2 mos
Babinski: May be present until 1 year of age, though some controversy exists. Abnormal if easily elicited, asymmetrical, or associated with other abnormal signs. Represents upper motor neuron lesions.	—	—
Parachute: Infant held in horizontal position; rapidly moved downward. Reflex movement is arm extension. Tests upper extremity pyramidal function. Asymmetrical in hemiparesis.	6-7 mos	Becomes voluntary
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Table 8. Muscle Function and Nerve Supply
Muscle	Motion	Nerve Root
Deltoid	Shoulder abduction	C-5
Infraspinatus	Shoulder external rotation	C-5
Biceps	Elbow flexion	C-5,6
Extensor carpi radialis	Wrist extension	C-6
Extensor digitorum Triceps	Finger extension Elbow extension	C-7
Interossei and lumbricalis	Digitial abduction/ adduction	C-8, T-1
Quadriceps Iliopsoas Adductor group	Knee extension Hip flexion Thigh adduction	L-2,3,4
Tibialis anterior Extensor hallucis	Ankle dorsiflexion Great toe dorsiflexion	L-5
Gastrocnemius	Ankle plantar function	S-1
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Table 9. Motor Reflex and Nerve Supply
Reflex	Muscle	Nerve Root
Biceps tendon	Biceps	C-5,6
Triceps tendon	Triceps	C-7,8
Patellar tendon	Quadriceps	L-2,3,4
Achilles tendon	Gastrocnemius	S-1
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Identification and therapy of the specific causes of weakness that are life threatening, irreversible, or treatable is a high priority. As described by Jacobson,⁴ some of these causes are presented in Table 10.

Table 10. Pitfalls in the Diagnosis of Weakness
Impending Respiratory Failure	Irreversible neurologic Defect	Treatable Disorders
Acute inflammatory demyelinating disorder (AIDP) (e.g., Guillain Barré) Myasthenia gravis Botulism Tick paralysis Tetanus Progressive quadriplegia (spinal cord or brainstem compression) Progressive increased intracranial pressure	Spinal cord compression Expanding intracranial mass lesions CNS infarction	AIDP (IVIG, plasmapheresis) Myasthenia gravis (anticholinesterase inhibitors, IVIG, plasmapheresis, steroids, thymectomy) Endocrine and electrolyte disturbances Mass lesions of brain or spinal cord (surgery, chemotherapy, radiotherapy)
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Diagnostic Approach

The diagnostic approach to the acutely weak child depends on the child’s age, the presence of trauma, and the mode of presentation (the patient’s cardiovascular/respiratory stability and mental status). Laboratory tests and other tests to be considered are listed in Table 11. Tests are indicated and chosen either to assist in the stabilization of the unstable patient or to confirm a diagnostic impression generated by history and physical examination.

Table 11. Weakness: Diagnostic Studies
Study	Indication
CBC	Infection; anemia, basophilic stippling with lead toxicity
Electrolytes, including calcium, magnesium, phosphorus	Suspect electrolyte imbalance with metabolic, endocrine, toxic or renal disease
Glucose	Suspect hyper-, hypoglycemia
BUN, Creatinine	Renal disease, uremia
Erythrocyte sedimentation rate	Inflammatory disease
Urinalysis, urine myoglobin, urine porphyrins	Suspect trauma, porphyria, renal disease, rhabdomyolysis
Creatine phosphokinase— MM isoenzyme	Muscle inflammation; injury
Toxicology of blood and urine	Suspect toxin
Thyroid hormone levels	Suspect hypothyroidism
Cortisol levels	Suspect hypoadrenalism
Chest x-ray	Suspect hypoxia, pulmonary or cardiac disease
Electrocardiogram	Suspect dysrhythmia, cardiac disease
Cerebrospinal fluid analysis	Suspect CNS infection, inflammation
Antinuclear, anti-skeletal muscle, motor end plate antibodies	Suspect auto-immune disease
Magnetic resonance imaging of brain, spinal cord	Suspect CNS structural injury, stroke
Computed axial tomography of brain, spinal cord	Suspect CNS structural injury, stroke
Electroencephalogram	Suspect seizure activity, Todd’s paralysis
Electromyography	Muscle abnormality
Nerve conduction studies	Nerve abnormality
Muscle biopsy	Muscle structure abnormality
Bone marrow aspiration	Anemia, thrombocytopenia, leukemia
Coagulation studies (PT, PTT, platelet count)	Bleeding disorder
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Children younger than 18 months presenting with a history of weakness without trauma may arbitrarily be considered potentially unstable and should be evaluated accordingly. (See Table 12.) This reflects the age-related difficulties in mental status evaluation, sensory differentiation and quantitation, and general inability to cooperate with diagnostic efforts. Exceptions will, of course, exist. Even without a history of trauma, accidental or inflicted injury should be considered a possibility.

Table 12. Diagnostic Approach to Weakness

The Unstable Patient

Life support — The ABCs
Pulse oximetry/ABG
CXR
ECG
Electrolytes and glucose
If alteration of mental status, toxicology, CT/MRI brain scan

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Children with a history of trauma who are stable may be evaluated with the appropriate imaging studies and lab studies of the affected area (e.g., brain, spine, or extremity).

Unstable patients (including those under 18 months) deserve an evaluation that obviates sepsis/meningitis, congestive heart failure, hypoxemia, increased intracranial pressure, intoxication, occult trauma, and glucose or electrolyte abnormality. Once these life-threatening problems are ruled out, a more detailed and focused exam, which looks for primary neurologic or muscle disease, can then be undertaken.

The stable patient older than 18 months may be evaluated initially with a focused neurologic and musculoskeletal exam. Clinical clues to the origin of neuromuscular illness are noted in Table 13. The neuromuscular evaluation should begin with an attempt to characterize the origin of weakness as upper motor neuron vs. lower motor neuron.

Table 13. Lower Motor Neuron Pathologic Signs¹⁰
Quality	Motor Neuron	Nerve	Junction	Muscle
Sensation	Normal	Normal/Decreased	Normal	Normal
Strength	Decreased	Decreased	Normal/Decreased	Decreased
Tone	Decreased	Decreased	Normal/Decreased	Decreased
Muscle Bulk	Decreased	Decreased	Normal/Decreased	Normal/Decreased
Fasciculations	Present	Present	Absent	Absent
Reflexes	Absent	Absent	Normal/Decreased	Absent/Decreased
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Upper motor neuron lesions produce increased tone (flexor in upper extremities, extensor in lower extremities); weakness; hyperreflexia; and extensor plantar responses. The pathologic process involves either the brain or spinal cord. Cranial nerve evaluation and sensory exam will usually pinpoint a clear level. Neck pain or cervical sensory findings suggest a high cord lesion. Unilateral facial weakness with hemiparesis suggests a brain lesion above the seventh nerve nucleus. Sometimes either MRI, CT, EEG, and/or CSF analysis may be required to clarify the problem.

Lower motor neuron lesions imply disease of the motor unit: motor neuron, nerve, neuromuscular junction, or muscle. Table 14 assists in localization of a lower motor neuron lesion.

Table 14. Clarifying and Localizing the Symptom of Weakness: Some Important Distinctions
Points of Distinction	Clinical Meaning
Upper motor neuron vs. lower motor neuron	Central nervous system vs. peripheral nervous system*
Voluntary vs. involuntary	Malingering, conversion**
Abnormal mental status vs. uncooperativeness	Systemic or central vs. peripheral lesion
True weakness vs. pseudo-weakness	Pain is interpreted as weakness
Tender vs. non-tender	Pseudo-weakness
Painful vs. non-painful	Pseudo-weakness
Abnormal sensation vs. normal sensation	Segmental sensory loss suggests cord level injury
Ataxia vs. weakness	Coordination problem mimics weakness
Vertigo vs. weakness	Vestibular or cerebellar problem mimics weakness
Asymmetry or symmetry	Unilateral vs. bilateral cerebral lesion
(Hemiparesis vs. quadriparesis)	(Symmetric quadriparesis may also result from lesions of the upper cervical cord or lower brain stem)
Upper extremity vs. lower extremity	Preferential lower extremity (paraparesis) involvement suggests a spinal cord lesion
Upper extremity only vs. upper and lower extremity	Peripheral nerve vs. central lesion
Unilateral vs. bilateral	Hemiparesis or peripheral nerve vs. central nerve
Sphincter or sacral involvement	Spinal cord lesion
Proximal vs. distal muscle involvement	Myopathy vs. neuropathy
* Upper motor neuron findings: Increased tone (flexor in upper extremities, extensor in lower extremities); weakness; hyperreflexia; extensor plantar responses. ** Rare in child younger than 10 years of age. Two helpful tests for malingering include: Hoover’s sign: The supine patient, when directed to press a leg downward, will involuntarily lift the other leg. This is absent in the malingerer. Beevor’s sign: In paralysis of the lower parts of the recti abdominis, there is upward excursion of the umbilicus with attempted leg movement. This is absent in the malingerer. __________________________________________________________________________________________

Management

Management priorities include three levels of intervention: The initial approach is directed at life support. Anticipation, assessment, and treatment of possible respiratory failure and shock can be accomplished through the guidelines of Pediatric Advanced Life Support.⁹ The second level of intervention is disease-specific therapy. Infections such as lyme disease, Mycoplasma pneumonia, meningitis, and diphtheria require appropriate antibiotic therapy. Epidural abscesses or acute head trauma require a consultation with a neurosurgeon. All fracture/subluxation should be reduced and the patient reassessed for return of function. All metabolic abnormalities should be corrected (hyponatremia, hyperkalemia, hypocalcemia). Hormone replacement therapy should be initiated in patients with DM, hypoadrenalism, and hypothyroidism. For suspected toxin ingestions, reversal agents should be identified and used when appropriate. The third level of intervention is determination of appropriate disposition.

Additional Aspects

The Floppy Infant. A special situation of pediatric weakness is that of the infant, the so-called "floppy" or "hypotonic" infant. The clinical approach is the same as that outlined above for the older child regarding anatomic localization. The differential diagnosis is somewhat different, and the safety margin for diagnostic error is significantly narrower. (See Table 15.) Age-related immune compromise in the first month of life predisposes the newborn to illnesses that typically don’t occur in adults. Botulism, for example, is caused by the ingestion of preformed toxin in the adult. It appears that merely ingesting the C. botulinum spores is sufficient to allow in vivo production of the toxin in small infants. The non-specific, mild, clinical manifestations of serious illness in this age group suggests an aggressive, closely-monitored diagnostic process with a high index of suspicion for such serious systemic entities as sepsis, congestive heart failure, and status epilepticus. As with the older child, common, treatable, systemic disease considerations include electrolyte abnormalities (including Na, K, Mg, Ca, and P), renal acidosis, uremia, scurvy, rickets, and hypothyroidism.

Table 15. The Floppy Infant
Anatomic Site	Pathology	Clinical Findings
Cerebrum	Idiopathic mental retardation Atonic diplegia	Hyperreflexia Extensor plantar reflex
Basal ganglia	Choreoathetotic cerebral palsy Kernicterus	Dystonia Choreoathetosis
Cerebellum	Ataxic cerebral palsy	Ataxia Hyporeflexia
Spinal cord	Cervical cord injury at delivery	Hyperreflexia; Sensory level Extensor plantar reflex
Anterior horn cell	Werdnig-Hoffman disease; Polio; Glycogen storage disease Type II	Areflexia; Normal sensation
Nerve	Neuropathy, usually metabolic	Hyporeflexia; Slowed nerve conduction time
Neuromuscular junction	Myasthenia gravis Drugs; Infant botulism	Positive edrophonium test
Muscle	Muscular dystrophy, myopathy	Elevated muscle enzymes
Connective tissue	Connective tissue disease	Normal muscle, nerve exam
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Guillain-Barré Syndrome. Guillain-Barré syndrome deserves special mention as the most common cause of acute generalized paralysis in all age groups. It is very rare in children younger than 1 year of age. The incidence in children younger than 4 years is 1.7/100,000. The illness presents as progressive muscle weakness with decreased deep tendon reflexes with symmetric distribution. The weakness is usually progressively ascending, beginning in the legs and extending to the arms. Accompanying sensory loss may be present in 40% of patients. The syndrome may initially present as a gait disturbance. Fifteen to twenty percent of patients progress to respiratory failure. The autonomic nervous system may be affected, sometimes causing cardiovascular instability via dysrhythmia or hypotension. There are typically three stages to the syndrome: 1) Progression phase, lasting a few days to a few weeks; 2) Plateau phase, also lasting a few days to a few weeks; and 3) Recovery phase, lasting weeks to months. Laboratory testing may include CSF analysis, showing elevated protein and normal cell count; electrodiagnostics, showing a reduction in the compound muscle action potential and distal latency prolongation; and electromyography, showing only an initial reduction in recruitment. In the acute phase, the main therapeutic concern is supportive care, primarily tending to the possibility of respiratory failure. Plasma exchange and or intravenous immune globulin may be indicated in rapidly progressive or otherwise severe cases.

Disposition

Disposition is predicated on diagnosis. The entities presented in Table 10 require admission and intensive observation and care. Other categories of patients that might require admission include:
• Any unstable patient;
• Any stable patient with uncertain diagnosis and possibility of progression;
• Any patient with requirement for nursing care;
• Any patient with requirement for hospital technology;
• Any patient with specialized equipment requirements;
• Any patient with medication preparation/administration;
• Any patient with parental inadequacy/fear/inability/ unwillingness to manage problem at home.

Home management of patients with stable weakness may be an option if home health care services are available. This also requires the informed, educated agreement of parents who are adequate, comfortable, able, and willing to manage the problem with the assistance of home health care personnel.

For those other diagnoses that threaten neither life nor limb, the capability of the family can be assessed by consideration of the following potential variables:

Patient age
Mother
Siblings
Funding
Certainty of diagnosis
Primary care
Medications required
Ancillary support (home health care)
Infusion
Occupational therapy

Family support system
Father
Respite
Stability of problem
Follow-up
Subspecialist
Equipment required
Respiratory
Physical therapy
School support

Summary

History and physical examination, elicited with an appreciation for the unique development-dependent presentation of illness in childhood, will reveal the cause of acute weakness in most children. The judicious choice of lab and imaging studies will assist in confirmation of the diagnosis. Hospitalization is indicated for those patients who are unstable and for those with uncertain diagnosis. Prioritized therapeutic intervention, guided by the principles of pediatric advanced life support, and supplemented by disease-specific care, will stabilize patients and allow for transfer from the emergency setting to the appropriate source of definitive care.

Glossary of Illnesses in the Differential Diagnosis of Weakness

Acute inflammatory demyelinating polyradiculoneuropathy (AIDP) (see Guillain-Barré): immune-related inflammation of peripheral nerves, frequently after viral infection.

Asthma: Patients may experience neuropathy (Hopkin’s syndrome¹⁶) or myopathy¹⁴ (steroid or or neuromuscular blocking agent treatment) in the course of asthma exacerbation.

Botulism: neuroparalytic disorder caused by toxin of Clostridium botulinum from contaminated canned food, wound infection or from ingested spores in infants. Distinct for its involvement of cranial nerves.

Calcium: Increased or decreased levels may produce weakness. Renal disease, hyper- and hypoparathyroidism, diuretics and sodium phosphate enemas are among the causes.

Campylobacter jejuni: Implicated as an antecedent illness in Guillain-Barré syndrome

Child abuse: A frequently occult presentation of central nervous system injury, spinal cord injury, or pseudoparalysis from musculoskeletal injury.

Ciguatera: A toxin harbored by barracuda, mahi mahi, and grouper that causes gastroenteritis and acute demyelinating neuropathy.

Dermatomyositis: A non-suppurative, immune-mediated inflammation of skin, subcutaneous tissue, and underlying muscle. Heliotrope discoloration of bridge of nose, erythematous or exfoliative rashes, Raynaud’s phenomenon, proximal muscle weakness and stiffness, synovial and tendon friction rubs, lymphadenopathy, and splenomegaly.

Devic’s disease (neuromyelitis optica): Massive, acute demyelination of optic nerves and spinal cord. A variant of the fulminant form of multiple sclerosis.

Diphtheria: May cause polyneuropathy as delayed complication of primary pharyngeal infection. Stocking-glove sensory loss, ptosis, and dysphagia. May be accompanied by myocarditis. History of inadequate immunization.

Duchenne muscular dystrophy: The most common form of muscular dystrophy.

Dysbarism: Neurologic or musculoskeletal injuries secondary to breathing compressed gases at higher than normal atmospheric pressure.

Eaton-Lambert syndrome: Antibody-mediated decrease in the Ach release sites of the presynaptic membranes of neuromuscular junction. Most commonly associated with malignancy.

Fisher syndrome: See Miller-Fisher syndrome.

Glycogen storage disease: See McArdle’s disease.

Guillain-Barré syndrome; Landry-Guillain-Barré syndrome: See AIDP.

Heavy metals: Cause peripheral neuropathy usually associated with encephalopathy.

Hopkins syndrome: Poliomyelitis-like illness associated with asthma.

Magnesium: Increased or decreased values associated with weakness. Seen with diuretics, malnourishment, hypokalemia, renal disease, malabsorption, GI fistula, ketoacidosis, burns, and sepsis,

McArdle’s Disease: A glycogen storage disease secondary to an inherited absence of muscle phosphorylase resulting in defective glycogenolysis in muscle cells.

Miller-Fisher syndrome: Guillain-Barré variant with cranial nerve involvement.

Multiple sclerosis: Spotty, immune-mediated demyelination of the nervous system.

Munchausen syndrome by proxy: Factitious illness in a child caused by an adult. Includes poisoning, electrolyte disorders, vomiting, diarrhea, suffocation, seizures, failure to thrive, among others.

Muscular dystrophy: Hereditary muscle disease with gradual onset early in life, involvement of proximal more than distal muscles, loss of deep tendon reflexes, and pseudohypertrophy of muscle. Six major clinical forms: Duchenne, Becker, Emery-Driefuss (humeroperoneal), Landouzy-Dejerine (fascioscapulohumeral), and limb-girdle dystrophies.

Myalgia cruris epidemica: The inflammatory, viral myositis that occurs, mainly in calf muscles, in association with epidemics of influenza.

Myasthenia gravis: Most common disease of neuromuscular junction. Autoimmune antibodies against Ach receptor. Presents with easy fatigability, especially extraocular muscle weakness sparing pupils. Diagnosis by edrophonium test.

Myopathies, congenital: Hereditary muscle abnormalities of unknown origin that usually present in infancy and require biopsy for diagnosis. They include Central Core Disease, nemaline, myopathy, and myotubular (centronuclear), myopathy

Neuropathy, congenital: Hereditary motor and sensory neuropathies of unknown origin that present in infancy with generalized weakness, hypotonicity, and areflexia. They include Charcot-Marie-Tooth Disease and Dejerine-Sottas Disease. Two inherited acute, focal neuropathies that occur later in life are inherited brachial plexus neuropathy and tomaculous neuropathy.

Paralytic shellfish poisoning: Ingestion of mollusk (clams, oysters, mussels, scallops) that have accumulated toxic concentrations of red-pigmented, marine dinoflaggellates (plankton) during periods of extreme proliferation ("red tide"). The paralytic neurotoxin (saxitoxin) may cause symptoms within 30 minutes, including dysesthesias, tremors, fasiculations, seizures, and paralysis, with respiratory paralysis sometimes occurring.

Periodic paralysis: Episodic hyper- or hypokalemia, frequently precipitated by exercise or a large meal. May be associated with hyperthyroidism.

Phosphate: Rarely isolated electrolyte disorder, may be seen with prolonged intravenous therapy and malnutrition.

Poliomyelitis: Febrile illness with CSF pleocytosis. Secondary to failure to vaccinate or oral vaccine complication. Occurs as spinal, bulbar and encephalitic forms. May show asymmetric, scattered, flaccid paralysis after an initial painful, tender muscle symptoms

Polymyositis: Inflammatory, immune-mediated disease of skeletal muscles; rhabdomyolysis occurs rarely. Similar to dermatomyositis without skin manifestations.

Porphyria: Present with abdominal pain, nausea, vomiting, muscle spasm, peripheral neuritis, photosensitization, skin pigmentation.

Potassium: From acidosis, renal failure, iatrogenic, crush/rhabdomyolysis, Addison’s disease, periodic paralysis, and drugs (potassium-sparing diuretics, NSAIDS, digitalis).

Puffer fish: Harbors tetrodotoxin, a sodium channel blocker.

Sodium: Affected by GI losses, renal disease, iatrogenesis, adrenal insufficiency, and third-spacing.

Tetrodon poisoning: See Puffer fish.

Thyroid disease: Childhood onset hypothyroidism may present with weak, pseudohypertrophic muscles, in association with impaired memory, poor school performance, generalized slowing of movement and speech.

Tick paralysis: Common dog tick (Dermacentor variablis) or wood tick (Dermacentor andersoni) envenomation with toxin affecting neuromuscular junction. Usually an ascending weakness with areflexia.

Todd’s paralysis: Postictal paralysis.

Transverse myelitis: Acute inflammatory spinal cord demyelination. When associated with optic neuritis, termed Devic’s disease.

Werdnig-Hoffman disease: Infantile spinal muscular atrophy from degeneration of anterior horn cell. Inherited as an autosomal recessive trait.

References

1. Tabor’s Cyclopedic Medical Dictionary. Thomas CL, ed. 15th ed. Philadelphia: F.A. Davis Company; 1985.

2. Mellick LS. Pearls and pitfalls of pediatric assessment: Secrets for approaching children in the emergency department. Emergency Medicine Reports 1994;15:19-30.

3. Nass R. Rapid assessment of mental status in the infant and young child. Ped Clin NA 1987;5:739-750.

4. Jacobson RD. Approach to the child with clumsiness or weakness. Ped Clin N A 1998;45;145-168.

5. Pediatric Neurology for the House Officer. Weiner HL, Bresnan MJ, Levitt LP. Baltimore: The Williams & Wilkins Company; 1977.

6. First LR, Palfrey JS. The infant or young child with developmental delay. N Engl J Med 1994;330:478-483.

7. Tindall B. Aids to exam of the peripheral nervous system. Oxford: Alden Press; 1986.

9. Pediatric Advanced Life Support. American Heart Association/American Academy of Pediatrics. 1997.

10. Crawford TO. Clinical evaluation of the floppy infant. Pediatr Ann 1992;21:348-354.

Acute Presentation of Muscle Weakness

Acute Presentation of Muscle Weakness

Definition of the Problem

Etiology

Pathophysiology

Clinical Features

Diagnostic Approach

Management

Additional Aspects

Disposition

Summary

Glossary of Illnesses in the Differential Diagnosis of Weakness

References

Recommended Reading