CMT 1A: Diabetes Mellitus Exacerbates Motor and Sensory Impairment

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Diabetes Mellitus Exacerbates Motor and Sensory Impairment in CMT1A

(AAN April 17, 2008)

Soham G. Sheth, Francies, Carly Siskind, ,

E. Shy, Detroit, MI

OBJECTIVE: Determine whether Diabetes Mellitus exacerbates Charcot

Marie Tooth disease type 1A (CMT1A).

BACKGROUND: CMT1A is caused by a duplication of the PMP22 gene on

chromosome 17 and is most common inherited demyelinating neuropathy

affecting 1:5000 people. Diabetes frequently causes predominantly

sensory neuropathy. Whether diabetes exacerbates CMT1A is unknown.

DESIGN/METHODS: We identified 8 patients with CMT1A AND diabetes and

compared their impairment with 48 age matched control patients with

CMT1A alone. Comparisons were made with the CMT Neuropathy Score

(CMTNS) and by electrophysiology.

RESULTS: The CMTNS was significantly higher in patients with

diabetes (20.25 + 2.35) compared to controls (15.19 + 0.69; p 0.01).

Values were higher for both motor and sensory scores for diabetic

patients. Five of the 8 diabetic patients had CMTNS >20 (severe CMT)

while only 7 of the 48 age-matched controls had scores>20. There was

a trend of CMT1A patients with diabetes to have low compound muscle

action potentials (ulnar CMAP in cases recorded at ADM: 2.23 + 0.8;

controls: 3.24 + 0.3; p 0.25) although NCV were not slower in

diabetic patients compared with controls (ulnar CV in cases: 25.4 +

2.9; controls: 20.5 + 0.98; p 0.09).

CONCLUSIONS/RELEVANCE: Diabetes is likely to exacerbate both motor

and sensory impairment of patients with CMT1A, perhaps by increasing

axonal degeneration based on lower CMAP amplitudes in diabetic

patients. Control of diabetes should be particularly emphasized in

patients with concomitant CMT1A.