Hashimoto Encephalopathy: Syndrome or Coincidence?
Abstracts & Commentary
Sources: Taylor SE, et al. An organic cause of neuropsychiatric illness in adolescence. Lancet. 2003;361:572; Chong JY, et al. Hashimoto encephalopathy. Syndrome or myth? Arch Neurol. 2003;60:164-171.
Taylor and associates report a case of Hashimoto encephalopathy in an adolescent girl with a 9-month history of what was initially diagnosed as chronic fatigue syndrome. Her illness included episodic neurological symptoms (altered consciousness, mild cognitive impairment, tremor, myoclonus, and a generalized seizure) as well as psychiatric features (mood swings, panic attacks, delusions, and hallucinations). The only abnormal laboratory tests were raised antithyroid microsomal antibodies and weakly positive antinuclear antibodies. EEG showed diffuse background slowing, and CSF protein was elevated (57 mg/dL). All symptoms resolved within 3 days of starting intravenous glucocorticosteroids in high dosage. Therefore, Taylor et al recommend that chronic fatigue syndrome be diagnosed with caution in adolescents, especially when there are associated neurologic signs and psychopathology. In such cases, Hashimoto encephalopathy should be a diagnostic consideration.
Chong and colleagues report a 63-year-old woman whose subacute onset of cognitive impairment, ataxia, and headache prompted a diagnosis of viral encephalitis. Symptoms improved with empirical antiviral treatment, but some months later she developed increasing confusion, tremor, generalized seizures, and coma. Brain MRI showed diffuse, nonenhancing white matter hyperintensity. There was a CSF leukocytosis of 26 cells per mm3, and the CSF protein was 98 mg/dL. Brain biopsy was nondiagnostic. A diagnosis of Hashimoto encephalopathy was made on the basis of elevated serum antithyroid microsomal antibody concentrations. The patient gradually improved with chronic glucocorticoid therapy and was neurologically normal 15 months later.
In a review of the literature, Chong et al identified 85 patients with encephalopathy and high serum antithyroid antibody concentrations (see Table 1). The mean age at onset was 44 years (range, 9-78 years). Nineteen were boys or girls 18 years or younger. Among the adults, there were 53 women and 13 men.
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Table 1. |
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Hashimoto Encephalopathy: Clinical Features in 85 Patients |
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| Clinical Feature | Patients | |
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n | (%) |
| Focal Deficit | 23 | 27 |
| Seizures | 56 | 60 |
| Psychosis | 31 | 36 |
| Relapsing-Remitting Course | 51 | 60 |
| High CSF Protein Concentration | 66 | 78 |
| Abnormal Brain Imaging | 40/82 | 49 |
| Abnormal EEG | 80/82 | 98 |
| Response to Glucocorticoids | 67/70 | 96 |
Neurologic symptoms were similar in all patients whether they were euthyroid, being treated with levothyroxine, or were hypothyroid. Serum concentrations of thyroid antibodies varied widely, and there was no relationship between neurologic symptoms and signs and the type or serum concentration of antithyroid antibodies (see Table 2).
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Table 2. |
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Thyroid Dysfunction in 85 Patients |
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| Category | n | % |
| Euthyroid | 26 | 31 |
| Hypothyroid | 48 | 56 |
| Hyperthyroid | 6 | 7 |
| Not Reported | 5 | 6 |
| Anti-M1 present | 55/58 | 95 |
| Anti-TPO2 present | 26/26 | 100 |
| Anti-Tg3 present | 45/62 | 73 |
| References | ||
| 1. Antithyroid microsomal antibody | ||
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2. Antithyroid peroxidase antibody |
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| 3. Antithyroglobulin antibody | ||
Based on their review of cases of Hashimoto encephalopathy, Chong et al concluded that the constellation of clinical manifestations constitutes a syndrome and that high serum antithyroid antibody concentrations are unlikely to be a chance association.
Commentary
Hashimoto encephalopathy is associated with high serum antithyroid antibody concentrations, but there is no evidence that these antibodies have a role in the pathogenesis of the cerebral disease. Chong et al point out that patients with autoimmune disease often have high serum concentrations of one or more antibodies directed against tissues not affected by the particular autoimmune disease. Therefore, the presence of high serum antithyroid antibody concentrations in Hashimoto patients could be another example of this autoimmune phenomenon, rather than indicating that the antibodies have a causal relationship to the encephalopathy.
One can conclude, however, that Hashimoto encephalopathy is a distinct clinical syndrome that is identified by and linked to the presence of high serum antithyroid antibody concentrations. — John J. Caronna
Taylor and associates report a case of Hashimoto encephalopathy in an adolescent girl with a 9-month history of what was initially diagnosed as chronic fatigue syndrome.You have reached your article limit for the month. Subscribe now to access this article plus other member-only content.
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