Clinical, electrophysiologic, and pathologic evidence for sensory abnormalities in ALS

Background: Amyotrophic lateral sclerosis (ALS) is a progressive degenerative disease of upper and lower motor neurons. Reports of the nature and frequency of sensory nerve involvement in ALS have varied. Methods: We reviewed the Emory University motor neuron disease registry between 1997 and 2004 to identify 103 patients with ALS without coexisting diseases that might cause sensory abnormalities and for whom electrodiagnostic studies were available for review. Neurophysiologic studies were interpreted based on age-adjusted normative data from our laboratory. Twelve control biopsies were evaluated alongside 22 samples from patients with ALS to ensure blinded evaluation of pathologic specimens. Results: Sensory symptoms or signs were present in 32% of patients, sural sensory nerve action potential amplitudes were abnormal in 27%, and pathologic abnormalities were present in 91% of patients. Large-caliber myelinated fibers were predominantly affected (reduced in 73%) and small-caliber myelinated fibers were affected less often (23%). Thinly myelinated fibers were present in 95% and regenerating clusters in 77% of the biopsies. Teased fiber analysis showed an increased frequency of axonal degeneration and regeneration as well as excessive myelin irregularity. Morphometry confirmed the loss of large-caliber fibers. Conclusions: These data indicate that one third of patients with amyotrophic lateral sclerosis report sensory symptoms and sural sensory response amplitudes are reduced in a similar proportion of subjects. Pathologic evidence of sensory nerve pathology was present in 91% of patients who underwent sural nerve biopsy. The electrophysiologic and pathologic findings indicate a pattern of axonal loss that predominantly affects large-caliber myelinated fibers.