A 52-year-old man presents with a 4-month history of progressive symmetric weakness in both legs and arms, along with loss of vibration sense and proprioception. Examination reveals areflexia and distal wasting. MRI of the spine shows the finding marked **A** in the diagram. Nerve conduction studies demonstrate prolonged distal motor latencies, slow conduction velocities, and conduction blocks in multiple nerves. CSF analysis shows protein elevation with <5 cells/μL. Based on these findings, what is the most likely diagnosis?
A. Anti-MAG neuropathy
B. Chronic Inflammatory Demyelinating Polyneuropathy (CIDP)
C. Guillain-Barré Syndrome (GBS)
D. Diabetic distal sensorimotor polyneuropathy
Explanation
Why Chronic Inflammatory Demyelinating Polyneuropathy (CIDP) is right
The clinical presentation—progressive symmetric proximal and distal weakness over 4 months (>8 weeks), areflexia, large-fiber sensory loss (vibration/proprioception), electrodiagnostic evidence of demyelination (prolonged distal latencies, slow conduction velocities, conduction blocks), and CSF albuminocytologic dissociation—all satisfy EFNS/PNS 2021 CIDP diagnostic criteria. The MRI finding of hypertrophic nerve roots and cauda equina thickening (marked A) is a hallmark supportive feature of CIDP, reflecting chronic demyelination with Schwann cell proliferation (onion bulb formation). CIDP is the chronic counterpart of GBS, distinguished by disease duration >8 weeks and the characteristic imaging findings of hypertrophic, enhancing nerve roots.
Why each distractor is wrong
Guillain-Barré Syndrome (GBS): GBS has a rapid onset and progression within <4 weeks, whereas this patient's symptoms evolved over 4 months. GBS also typically features autonomic dysfunction (not present here) and does not show hypertrophic nerve roots on MRI. The chronic progressive course rules out GBS.
Diabetic distal sensorimotor polyneuropathy: Diabetic neuropathy is characteristically distal-predominant and does not involve proximal muscles significantly. There is no mention of diabetes, and the symmetric proximal involvement is atypical for diabetes. Electrodiagnostic findings in diabetes show axonal loss, not demyelination with conduction blocks.
Anti-MAG neuropathy: Anti-MAG neuropathy is a demyelinating condition but is typically distal-predominant, affects the lower limbs more than upper limbs, and often presents with tremor. Proximal weakness is not a feature, and hypertrophic nerve roots are not characteristic. It is a variant/mimic of CIDP but does not fit this clinical picture.
