Sensory Cortex Hyperexcitability Predicts Shorter Survival in ALS

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Subclinical sensory neuron dysfunction in the central and peripheral nervous systems has been identified in patients with ALS.
Subclinical sensory neuron dysfunction in the central and peripheral nervous systems has been identified in patients with ALS.

Sensory cortex hyperexcitability is associated with shorter survival among patients with amyotrophic lateral sclerosis (ALS) and may serve as a prognostic indicator in these patients, according to study findings published in Neurology.

Investigators obtained patient data from a neurophysiology laboratory in Tokyo, Japan, which included 145 patients with sporadic ALS who were examined with median nerve somatosensory evoked potential (SSEP) testing. A total of 73 age- and sex-matched healthy controls were also included in the analysis. AgCl electrodes were placed to evaluate N9 (Erb-Fz), N13 (CS5-Fz), N20 (CP-Fz), P25 (CP-Fz), and N33 (CP-Fz). The investigators measured onset-to-peak amplitude of N13 and N20 and peak-to-peak amplitude between N20 and P25 (N20p-P25p).

Additionally, the investigators clinically staged patients based on the ALS Functional Rating Scale-Revised and classified patients based on the site of disease onset. Patients were followed up to death or tracheostomy, whichever came first.

Patients with ALS demonstrated larger onset-to-peak amplitude of N13-P25p in the median nerve SSEP compared with healthy controls. The median survival time was shorter in patients with N20p-P25p ≥8 μV compared with patients with N20p-P25p <8 μV (0.82 years vs 1.68 years; P =.0002). A larger amplitude of N20p-P25p was significantly associated with shorter survival in multivariate analysis (P =.002).

Limitations of this study include its small sample size and the limited generalizability of the findings outside of Japanese patients.

According to the investigators, a possible mechanism associated with the increased N20p-P25p in patients with ALS “is a compensatory or neuroplastic change within the sensory cortex that is associated with excitability or degenerative changes of the motor cortex.”

Reference

Shimizu T, Bokuda K, Kimura H, et al. Sensory cortex hyperexcitability predicts short survival in amyotrophic lateral sclerosis [published online March 30, 2018]. Neurology. doi: 10.1212/WNL.0000000000005424

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