Terminal latency index in neuropathy with antibodies against myelin-associated g

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Muscle Nerve. 2006 Oct 26

Terminal latency index in neuropathy with antibodies against myelin-

associated glycoproteins.

Lupu VD, Mora CA, Dambrosia J, Meer J, Dalakas M, Floeter MK.

EMG Section, National Institute of Neurological Disorders and

Stroke, National Institutes of Health, Building 10, CRC, 7-5680, 10

Center Drive, Bethesda, land 20892, USA.

Neuropathy with antibodies against myelin-associated glycoproteins

(MAG/SGPG-N) and hereditary sensorimotor neuropathy type 1 (HMSN1)

are characterized by chronic demyelination with little conduction

block. Electrodiagnostic studies suggest that in HMSN1 conduction

slowing occurs uniformly along the nerve, whereas in MAG/SGPG-N it

is predominantly distal. Some but not all previous reports have

shown that the terminal latency index (TLI) was useful to

distinguish MAG/SGPG-N from chronic idiopathic demyelinating

polyneuropathy.

We compared median TLI from 21 patients with MAG/SGPG-N with those

obtained from 26 patients with HMSN1, 20 with HMSN2, and 12 healthy

volunteers. All patients with TLI <0.26 had MAG/SGPG-N, and all

patients with TLI >/=0.32 had HMSN1.

In the remaining patients with intermediate TLI values, ulnar distal

motor latency (DML) aided in differentiation between MAG/SGPG-N and

HMSN1 with an overall sensitivity of 100% and specificity of 98%.

In conclusion, median TLI in combination with ulnar DML can further

guide the demyelinating neuropathy evaluation toward hereditary or

autoimmune causes.