CLINICAL AND ELECTRODIAGNOSTIC FEATURES OF CHARCOT-MARIE-TOOTH SYNDROME

Motor conduction parameters in neuropathies associated with anti-MAG antibodies and other types of demyelinating and axonal neuropathies

We measured residual latency (RL), motor conduction velocity (MCV), and terminal latency index (TLI) in 15 patients with neuropathy and anti-MAG or SGPG antibodies and compared these to values obtained in 103 patients with other types of polyneuropathy (PN) and to 57 normal subjects. Ten patients had anti-MAG antibody titers of 25,600 or higher, and 5 had titers between 800 and 12,600. Patients with the highest titers had longer RL, slower MCV and shorter TLI than those with lower titers, acute or chronic inflammatory demyelinating PN, hereditary neuropathy, and metabolic or axonal neuropathy. In contrast F-wave latencies did not contribute to the differentiation between the groups of demyelinating neuropathies. RL and TLI correlated best with anti-MAG antibody titers, whereas there was a poor correlation with anti-SGPG titers suggesting that MAG more than SGPG may be the antigen in PN, and that the distal nerves are affected more than their proximal segments. The RL rather than TLI turned out to be the best variable to classify the demyelinating type of anti-MAG neuropathy. Sural nerve biopsy in 5 of the patients with the highest titer of anti-MAG antibodies showed deposits of IgM and C3 on the myelin sheaths, pronounced demyelination and widening of the myelin lamellae. In 4 of the patients with lower titers demyelination was absent or less pronounced.

Genetic disorders that masquerade as multiple sclerosis

There are many genetic disorders that have signs and symptoms suggestive of multiple sclerosis and that may easily be overlooked in the evaluation of both adult and pediatric multiple sclerosis patients. The recognition of a genetic disorder as the cause of a patient's "multiple sclerosis" phenotype has important implications not only for the patient, but often also for others in the patient's family who may be at risk for the same disease. We present here a review of single gene disorders that can masquerade as multiple sclerosis. For each disorder, the major clinical and biochemical characteristics are discussed, together with the appropriate testing to screen for and confirm the diagnosis. In addition, guidelines are presented for when to suspect an underlying genetic condition in a patient with a diagnosis of definite or probable multiple sclerosis. The great variety of genetic disorders that can masquerade as multiple sclerosis and the many implications of a genetic diagnosis underscore the importance of recognizing genocopies of multiple sclerosis.

Evidence for a recessive PMP22 point mutation in Charcot-Marie-Tooth disease type 1A

Charcot-Marie-Tooth disease type 1A (CMT1A) is an autosomal dominant neuropathy that can be caused by dominant point mutations in PMP22 which encodes a peripheral nerve myelin protein. Usually, CMT1A is caused by the duplication of a 1.5-megabase (Mb) region on chromosome 17p11.2-p12 containing PMP22. Deletion of a similar 1.5-Mb region is associated with hereditary neuropathy with liability to pressure palsies (HNPP), a clinically distinct neuropathy. We have identified a severely affected CMT1 patient who is a compound heterozygote for a recessive PMP22 point mutation, and a 1.5 Mb deletion in 17p11.2-p12. A son heterozygous for the PMP22 point mutation had no signs of neuropathy, while two others heterozygous for the deletion had HNPP, suggesting that point mutations in PMP22 can result in dominant and recessive alleles contributing to CMT1A.

Charcot-Marie-Tooth disease in northern Sweden: an epidemiological and clinical study

One hundred four cases of Charcot-Marie-Tooth disease (CMT) in 52 families were identified within a defined area in northern Sweden corresponding to a prevalence rate of 20.1 cases per 100,000 (Dec 31 1991) for all subtypes. The prevalence of CMT type I was 16.2 per 100,000. The distribution of cases was not uniform. The prevalence rate is compared with previous prevalence studies focusing on Charcot-Marie-Tooth disease or hereditary motor and sensory neuropathy (HMSN). Three patients were classified as the distal spinal muscular atrophy type of CMT and one patient was not possible to classify. For seventy-five patients, available to clinical examination within the study, data were collected as to age at onset, symptoms, clinical findings and degree of disability.

Peroneal muscular atrophy. Part 1. Clinical and electrophysiological study

144 patients with the clinical syndrome of peroneal muscular atrophy or Charcot-Marie-Tooth disease were studied. Thirteen were recognized as the spinal form of the disease since all had normal motor nerve conduction velocity and sensory nerve action potential. The remaining patients could be classified according to their values of motor conduction velocity for the median nerve. Two main groups were therefore identified: 55 patients whose nerve conduction was below 30 m/s belonged to group I, which corresponds to the previously reported hypertrophic form or hereditary motor sensory neuropathy (HMSN) type I. Sixty-four patients whose nerve conduction was above 40 m/s belonged to group II which corresponds in the majority of cases to the neuronal form or HMSN type II. Twelve patients could not be classified since the motor nerve conduction velocity for median nerve ranged between 30 and 40 m/s. These could belong to either of the two main groups or might form an intermediate group, the existence of which is discussed. Clinical genetic and electrophysiological features of the two main groups are discussed and compared.

Dominantly inherited peroneal muscular atrophy (hereditary motor and sensory neuropathy type I) in infancy and childhood

A detailed clinical and electrodiagnostic study has been undertaken of demyelinating polyneuropathy in 14 children (9 male, 5 female) from 11 sibships and their parents. The onset of symptoms was before the age of 2 years in 12 of the 14 children, and the condition in all cases was nonprogressive or very slowly progressive. In each case one of the parents had a slow motor nerve conduction velocity. Five of the 11 affected parents were completely asymptomatic. Electrodiagnostic studies in both parents of all children with demyelinating peripheral neuropathy are thus important to identify the dominantly inherited form of the disease.