Current perception threshold: an adjunctive test for detection of acquired demyelinating polyneuropathies

Area of Science:

• Neurology
• Neurophysiology

Background:

• Polyneuropathies are classified as demyelinating or axonal, with distinct patterns of nerve fiber involvement.
• Demyelinating polyneuropathies typically affect larger myelinated fibers proximally, while axonal polyneuropathies affect smaller fibers distally.
• Accurate differentiation is crucial for appropriate diagnosis and management.

Purpose of the Study:

• To evaluate the utility of Current Perception Threshold (CPT) testing in distinguishing between demyelinating and axonal polyneuropathies.
• To compare CPT findings with established diagnostic criteria for polyneuropathy.

Main Methods:

• Current Perception Threshold (CPT) testing was performed on ten patients with demyelinating polyneuropathy and ten with axonal polyneuropathy.
• CPT assessed sensory thresholds for A-beta (2,000 Hz), A-delta (250 Hz), and C fibers (5 Hz) bilaterally across C2, lateral antebrachial cutaneous, and sural nerve distributions.
• Analysis focused on side-to-side asymmetries, fiber type involvement, and fiber type ratios.

Main Results:

• CPT testing demonstrated 50% sensitivity and 100% specificity in detecting demyelinating polyneuropathies.
• The diagnostic performance was comparable to established motor nerve conduction studies.
• CPT testing successfully differentiated between demyelinating and axonal polyneuropathy patterns.

Conclusions:

• Current Perception Threshold (CPT) testing is a valuable tool for differentiating demyelinating from axonal polyneuropathies.
• CPT is particularly useful in patients with sensory symptoms where electrodiagnostic tests may be inconclusive or when patients decline nerve conduction studies.