Diagnosis:

The diagnosis is made based on clinical features of neuropathy supported by electrodiagnostic testing and isolation of the underlying neoplasm

Clinical features:

Painful from: spontaneous pain and mechanical hyperalgesia i.e. painful sensation provoked or exacerbated by pinprick sensation a.k.a. pinprick hyperalgesia or gentle tactile stimulation a.k.a. allodynia
Ataxic form: Romberg positive, impaired vibration and proprioception
Usually asymmetric and only mild motor symptoms if present

Findings on investigations:

+NCS+EMG:

• Sensory involvement>motor
• Reduced or absent SNAPs. Prolonged sensory nerve conduction velocity SCV, motor conduction velocity MCV and distal latency

+CSF analysis: increased protein usually
+/-onconeuronal antibodies: anti-Hu antibodies positive in most. Anti CV2 positive in some
+evidence of an underlying cancer

Pathology:

Dorsal root ganglion damage: loss of large diameter sensory nerve cell bodies. Secondary degeneration of axons in the dorsal columns and peripheral nerves.
Sural biopsy: reduced large myelinated fibres and in some reduced small myelinated fibres.

Investigations to consider:

CT chest, abdomen, pelvis: lung cancer, ovarian cancer
Breast exam, mammography: breast cancer

Related articles:

• Approach to weakness, neuromuscular disease patterns, mononeuropathy multiplex, polyneuropathy,
• Paraneoplastic vasculitic neuropathy PVN (paraneoplastic neuromyopathy)