Abnormal sensory evoked potentials in amyotrophic lateral sclerosis

Area of Science:

• Neurology
• Neurophysiology
• Clinical Neuroscience

Background:

• Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease primarily affecting motor neurons.
• While motor symptoms are predominant, sensory system involvement in ALS is increasingly recognized but not fully understood.
• Evoked potentials (EPs) are electrophysiological tests that measure the brain's response to sensory stimulation, offering objective measures of sensory pathway integrity.

Purpose of the Study:

• To investigate the prevalence and patterns of sensory nervous system dysfunction in patients with amyotrophic lateral sclerosis (ALS) using various evoked potential (EP) modalities.
• To determine if EP findings provide evidence of central nervous system (CNS) sensory involvement in ALS.
• To compare EP findings with clinical and pathological observations of sensory system involvement in ALS.

Main Methods:

• A retrospective review of sensory evoked potential (EP) findings was conducted in 17 patients diagnosed with amyotrophic lateral sclerosis (ALS).
• Somatosensory EPs (SSEPs) were assessed following lower- and upper-extremity stimulation.
• Brainstem auditory EPs (BAEPs) and pattern reversal visual EPs (VEPs) were also evaluated in subsets of patients.

Main Results:

• Abnormalities in somatosensory EPs were detected in 7 of 16 patients after lower-extremity stimulation and 2 of 16 after upper-extremity stimulation.
• Brainstem auditory EP abnormalities were identified in 2 of 12 patients.
• No abnormalities were observed in pattern reversal visual EPs among 12 patients, with overall 47% of all studied ALS patients exhibiting at least one EP abnormality.

Conclusions:

• Evoked potential (EP) testing demonstrates evidence of central nervous system (CNS) sensory dysfunction in a significant proportion of amyotrophic lateral sclerosis (ALS) patients.
• The frequency of EP-detected sensory abnormalities in ALS surpasses that typically observed through clinical examination or post-mortem pathology.
• These findings support the hypothesis of sensory system involvement in the pathophysiology of ALS, highlighting the utility of EPs in characterizing the full spectrum of the disease.