Neurotherapeutic Alerts
Muscle or Nerve Biopsy for Vasculitis
Source: Claussen GC, et al. Diagnostic value of nerve and muscle biopsy in suspected vasculitis cases. J Clin Neuromusc Dis 2000;1:117-123.
Based on a retrospective review of 115 nerve and muscle biopsies performed over 20 years to rule out or confirm vasculitis (101 cases) or peripheral neuropathy (14 cases), nerve biopsy appears more sensitive than muscle biopsy for the diagnosis of suspected vasculitis. All 115 patients—58 men and 57 women—underwent both nerve and muscle biopsy, the sural nerve in all, and the tibialis anterior, gastrocnemius, vastus lateralis, deltoid, or biceps as the chosen muscle, depending on clinical involvement. Vasculitis was defined as definite (active or inactive) or probable, and myositis was defined by the presence of muscle necrosis and perivascular or endomysial inflammatory cells.
Muscle never demonstrated vasculitis in the absence of nerve vasculitis, although in three cases the muscle was definite, whereas the nerve was only probable. In 26 cases, nerve but not muscle showed vasculitis. Sixteen (14%) showed myositis without vasculitis and in seven of these, vasculitis was found in nerve. Overall, 45 biopsies (39%) demonstrated vasculitis, significantly more often (P = 0.0001) in nerve (n = 45; 39%) than muscle (n = 19; 17%).
Commentary
The debate continues, with studies reporting either nerve or muscle biopsy as more sensitive for vasculitis. Until the dust settles, if ever, cases of suspected vasculitis require both nerve and muscle biopsy, particularly if electrodiagnostic studies show abnormal sural sensory nerve conduction studies. —mr
For the diagnosis of vasculitis:
a. nerve biopsy is definitely more sensitive than muscle for the diagnosis of suspected vasculitis.
b. nerve biopsy is definitely less sensitive than muscle for the diagnosis of suspected vasculitis.
c. neither nerve nor muscle biopsy is warranted.
d. it is most prudent to perform both muscle and nerve biopsy.
IVIG, not Pheresis, for GBS with Anti-GM1b Ganglioside
Source: Yuki N, et al. Clinical features and response to treatment in Guillain-Barré syndrome associated with antibodies to GM1b ganglioside. Ann Neurol 2000;47;314-321.
Among 132 guillain-barré syndrome (gbs) patients who participated in the Dutch GBS trial and for whom suitable pretreatment serum was available, 25 (19%) demonstrated high anti-GM1b antibody titers of the IgG (n = 15) or IgM (n = 14) isotype, or both (n = 4). Compared to GM1b antibody-negative patients, antibody-positive patients more frequently experienced preceding diarrhea and serologic evidence of recent C. jejuni infection, without antecedent evidence of CMV, EBV, or M. pneumoniae. Onset was more rapid, limb weakness more severe, distal weakness more prominent, recovery time more prolonged, and response to intravenous immunoglobulin (IVIG), compared to plasmapheresis, was significantly faster in the GM1b antibody-positive cases. Cranial nerve involvement, paresthesiae, and sensory deficits were less frequent, whereas electrodiagnostic findings were not significantly different in the antibody-positive or negative cases. Comparison IgG vs. IgM GM1b antibody-positive patients revealed that IgM positive cases did not differ from antibody-negative patients with respect to cranial and sensory nerve involvement and time to peak severity. GM1 and GM1b antibody-positive patients demonstrate similar clinical features, but identification of the specific anti-GM1b antibody in GBS may have therapeutic ramifications.
Commentary
The precise role of GM1 antibodies in GBS pathogenesis remains unclear. Their presence in sensory ganglia and sensory axons begs the question of why GBS has a predilection for motor involvement. GM1 antibody interference with sodium and potassium currents may result in conduction block (Waxman SG. Ann Neurol 1995;37:421-423), but their binding to nodes of Ranvier, activating the complement cascade, did not cause such block (Paparounas K. et al. Brain 1999;122:807-816). Perhaps axonal destruction ties these observations together, but if that were true, how would one explain rapid improvement in axonal GBS? Conceivably, reversible distal conduction block at the motor nerve terminal might generate the phenomenon (Kaji R. Brain 1999;122:797-798). Further study should clarify this present puzzle. —mr
Advice for Slap-Happy Electromyographers!
Source: Pohl M, et al. Insertion pain in needle electromyography can be reduced by simultaneous finger slapping. Neurology 2000;54:1201-1202.
Finger-slapping the patient’s skin adjacent to, and simutaneously with, needle insertion during electromyography (EMG) study significantly (P < 0.001) decreases the pain intensity of EMG study. Using a 100-mm visual analog scale among 77 patients, finger-slapping reduced pain from a mean of 13.8 mm to 6.7 mm on first insertion, and from 22 to 7.5 on second needle insertion. Should the patient forget to premedicate with analgesics (LaJoie WJ. Arch Phys Med Rehabil 1963;44:42-44), should audio analgesia be not available (Spence WR, et al. Arch Phys Med Rehabil 1966;47:771-774), or should monopolar needles simply not do the trick, this manueuver can’t hurt! One cautionary note: take care not to prick your slap-happy finger with the needle! —mr
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