How are sensory abnormalities managed in patients with Amyotrophic Lateral Sclerosis (ALS)?

Sensory Abnormalities in ALS: Clinical Recognition and Management

Sensory abnormalities occur in approximately one-third of ALS patients and should be actively screened for and managed symptomatically, though their presence does not exclude the diagnosis of ALS. 1, 2

Clinical Significance and Recognition

Sensory symptoms are present in 32% of ALS patients, despite ALS being traditionally considered a pure motor disease. 2 The key clinical approach involves:

• Perform thorough sensory examination including light touch, pinprick, vibration, and proprioception testing at diagnosis and during follow-up 1
• Recognize that sensory symptoms are often overshadowed by motor manifestations but remain pathologically relevant 3
• Understand that the sensory system is typically spared clinically, though subclinical involvement is common 4

Diagnostic Evaluation

When sensory symptoms are prominent, nerve conduction studies should be performed to detect abnormalities in sensory nerve conduction. 1, 5

Electrophysiological Findings:

• Abnormal sural sensory nerve action potential amplitudes occur in 27% of patients 2
• Reduced minimum conduction velocity can be detected in 50% of patients (9 of 18) even when standard amplitude and maximum conduction velocity appear normal 6
• Sensory nerve conduction abnormalities are found in 22.7% of patients, with 12.5% meeting criteria for electrophysiological polyneuropathy 7
• Large-caliber myelinated fibers are predominantly affected (reduced in 73% of biopsies), while small-caliber fibers are less commonly involved (23%) 2

Pathological Evidence:

Pathologic abnormalities in sensory nerves are present in 91% of ALS patients who undergo sural nerve biopsy, indicating widespread subclinical sensory involvement 2

Differential Diagnosis Considerations

Prominent early sensory symptoms with minimal motor involvement should prompt consideration of alternative diagnoses such as Guillain-Barré syndrome variants or other peripheral neuropathies 1. However:

• Sensory abnormalities do not exclude ALS diagnosis when typical motor findings are present 7
• Patients with ALS and sensory nerve abnormalities may represent a variant of ALS consistent with degeneration of both motor neurons and dorsal root ganglion cells 7

Management Approach

Actively screening for and identifying sensory neuropathy improves patient management through three mechanisms: 1

1. Explains sensory symptoms to patients, providing reassurance that these are part of the disease spectrum
2. Allows targeted symptomatic treatment for pain, paresthesias, or other sensory complaints
3. Prevents unnecessary diagnostic workup for alternative conditions once sensory involvement is recognized as part of ALS

Symptomatic Treatment Strategy:

• Address neuropathic pain with standard neuropathic pain medications when sensory symptoms are bothersome 1
• Provide patient education that sensory symptoms, while present, typically do not progress as rapidly as motor symptoms 3
• Monitor for progression of sensory findings during routine neurological assessments 5

Common Pitfalls to Avoid

• Do not dismiss the diagnosis of ALS solely because sensory abnormalities are present - up to one-third of patients have clinical sensory involvement 2
• Do not rely only on standard nerve conduction parameters - minimum conduction velocity may reveal abnormalities missed by conventional amplitude and latency measurements 6
• Do not assume sensory symptoms indicate a different diagnosis without evaluating the full clinical picture including motor neuron signs 7