Polyneuropathy work-up

Screening tests

Serum electrolytes, fasting glucose, HbA1c, protein, liver and thyroid function tests

vitamin B12, RBC folate, methylmalonic acid levels, serum lipoproteins, serum protein electrophoresis

CK

CBC with eosinophil count, ESR

ANA, ENA, RA

Urine: glucose, protein

EMG, NCVs

Chest X-ray

Specific investigations

Oral glucose tolerance test

Serum carotene, vitamin E, vitamin B6

Blood and urine organic acids, carnitine, lactate and pyruvate (mitochondrial disease)

ACE, anti-Ro, anti-La, c-ANCA (Wegener), p-ANCA (Churg-Strauss), cryoglobulins (if positive test for Hep C, collagen vascular screen, monoclonal antibodies)

Serology EBV, CMV, HSV, M. pneumonia, HIV, Lyme serology, VDRL, Hep B and C

Serum and urine protein electrophoresis and immunoelectrophoresis

Anti-neuronal antibodies (Hu, Yo), anti-gliadin antibodies, anti-ganglioside (GM₁) antibodies (MMN), anti-GQ1b antibodies, anti-myelin associated glycoprotein (MAG) antibodies (MGUS), antisulfatide antibodies.

α-galactosidase (Fabry disease), β-hexosaminidase

Salivary flow rate, Schirmer test, Rose Bengal test, labial gland biopsy (Sjögren syndrome)

Urine: Bence-Jones protein, prophyrins

Stool cultures C. jejuni

Heavy metals in blood and urine.

Bone scan, US pelvis, CT scan abdomen and chest, mammography (malignancy)

CSF: cell count, protein, immunoglobulin, OCBs

Autonomic function tests

Sural nerve biopsy (vasculitis, perineuritis, CIDP, MLD, CADASIL, HSMN, HNPP, KLD, leprosy, amyloidosis, sarcoidosis, toxic)

MRI brain (demyelinating disorders).

Peripheral nerve myelin protein PMP22 gene duplication (CMT type IA) or deletion (HNPP), CMT2 gene (MFN2) mutations (CMT2A), connexin 32 (CJB1) mutation (X-linked CMT), PO gene mutation, Parsonage Turner.

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