Differentiating CIDP, ALS, and GBS

Key Distinguishing Features

The temporal pattern of disease progression is a critical distinguishing feature, with GBS progressing rapidly over days to 4 weeks with areflexia, CIDP progressing over at least 8 weeks with areflexia, and ALS progressing over months to years with hyperreflexia and upper motor neuron signs 1
Areflexia or hyporeflexia points toward GBS or CIDP, while hyperreflexia with pathologic reflexes strongly suggests ALS 1, 2

Rapid progression (days to <4 weeks to nadir) is characteristic of GBS, typically reaching maximum disability within 2 weeks 1, 3
Progression >8 weeks from onset suggests CIDP, while slow, relentless progression over months to years is most likely ALS 2, 4, 5
Prominent sensory symptoms/signs support GBS or CIDP, while absent or minimal sensory involvement does not exclude GBS but is characteristic of ALS 1, 3, 4
The presence of upper motor neuron signs, such as spasticity, hyperreflexia, and extensor plantar responses, is pathognomonic for ALS 1, 2, 4

Albumino-cytological dissociation (elevated protein, normal cell count) in cerebrospinal fluid supports GBS or CIDP 1, 2, 4
Demyelinating features on electrodiagnostic studies confirm GBS (AIDP subtype) or CIDP, while axonal features suggest GBS (AMAN/AMSAN subtypes) or CIDP 1, 2, 6
Chronic denervation with reinnervation on electrodiagnostic studies supports CIDP over GBS and is characteristic of ALS 2, 5

Deterioration after 8 weeks from onset or three or more deteriorations suggests CIDP rather than GBS 5

Assuming normal reflexes rule out GBS, as pure motor variant and AMAN subtype can have normal or even exaggerated reflexes 3
Diagnosing GBS too quickly in slowly progressive cases, as progression >4 weeks should raise suspicion for CIDP or alternative diagnosis 1
Missing acute-onset CIDP, which can be overlooked if not monitored for deteriorations beyond 8 weeks 5
Overlooking sensory involvement in ALS, as ALS should not have sensory symptoms or signs 1, 4
Waiting for CSF or EMG before treating suspected GBS, as GBS is a clinical diagnosis and treatment should not be delayed for confirmatory testing in rapidly progressive cases 1, 2, 6