Longitudinal conduction studies in hereditary motor and sensory neuropathy type 1

Abstract

Motor conduction studies were performed serially in 10 patients, ages 10-62 years, with clinical and electrophysiological criteria of hereditary motor and sensory neuropathy type 1 (HMSN-1) over periods of 11-19 years. Median nerve conduction velocity (MNCV) and distal motor latency showed no significant change on serial studies. Mean median compound muscle action potential (CMAP) amplitude values, however, decreased 66% in 8 patients. Observed clinical progression in HMSN-1, over prolonged periods of time, was not associated with MNCV slowing. However, CMAP amplitude reduction, reflecting progressive axonal loss, correlated with clinical deterioration.

Comparison between Clinical Disabilities and Electrophysiological Values in Charcot-Marie-Tooth 1A Patients with PMP22 Duplication

“…A longitudinal study found that axonal involvement progressed in a time-dependent manner, and that axonal degeneration proceeded concomitantly with advancing disease 10,16. The age-dependent reduction in the CMAPs, and the increase in axonal degeneration and clinical disability observed in our study were also in good agreement with previous reports 15,29. Furthermore, the median nerve TLI did not differ between Korean CMT1A patients and healthy controls.…”

Clinical disease severity and axonal dysfunction in hereditary motor and sensory neuropathy Ia

“…In HMSN Ia, CMAP amplitude reduction and disease progression have been shown in childhood [2]. Two longitudinal studies demonstrated CMAP amplitude reductions over time during life in a mixed population of patients with HMSN I [7,33]. Together with the results of our study, these data suggest that disease progression in HMSN Ia is related to increasing axonal dysfunction.…”

“…The initial dysmyelination and the subsequent cycles of demyelination and remyelination lead to a kind of balance in myelination in the first decade of life. This is supported by human longitudinal electrophysiological studies showing that motor nerve conduction velocity, an electrophysiological marker of myelination, is already abnormal at 2 years of age [11,13], and remains stable from the age of 5 years onwards [20,33].…”

“…There is controversy about the natural course of HMSN Ia in adulthood in the literature. Previous studies have noted clinical deterioration [4,7,14,33,39], whereas this was not found in other studies [16,20]. In HMSN Ia, CMAP amplitude reduction and disease progression have been shown in childhood [2].…”

“…In univariate analysis, we also found a correlation between median nerve MNCV and physical disability, but multivariate analysis showed that axonal dysfunction, i. e., CMAP amplitude, was the most important contributor to physical disability. As in other studies, we used CMAP amplitudes as an indirect measurement for axonal dysfunction [2,7,15,23,33]. CMAP amplitude can be influenced by temporal dispersion and interpotential phase cancellation [22], but these phenomena only had a minor role in our patients as there was no significant influence on CMAP area and CMAP duration between distal and proximal stimulation of the median nerve.…”