Investigations

The investigations of note in peripheral neuropathy include:

• FBC
• ESR, CRP
• LFTs, GGT
• TFTs
• glucose
• creatinine
• plasma B12 and folate
• serum protein electrophoresis and immunoelectrophoresis
• urinalysis
• CXR

Subsequently, EMG and peripheral nerve conduction; if these are normal and assuming symptoms and signs are confined to the legs, question whether there is a lesion in the cauda equina.

Notes:

• other special investigations may include serum vitamin E concentrations, cryoglobulins, urinary heavy metals and porphyrins, antinuclear antibodies, rheumatoid factor, Sjogren's syndrome (SS) antibodies, (SS-A (anti-Ro) and SS-B (anti- La)), serology for Lyme disease and HIV, antiganglioside GM1 antibodies, Schirmer's test; if raised inflammatory markers and features of possible paraneoplastic peripheral neuropathy then further investigation for possible occult malignancy

Reference:

1. Mirian A, Aljohani Z, Grushka D, et al. Diagnosis and management of patients with polyneuropathy. CMAJ. 2023 Feb 13;195(6):E227-E233