Table 5.

General investigations for autonomic disorders

Blood investigations

1. Full blood count, renal function, calcium panel, liver panel

2. Fasting blood sugars and HbA1c

3. Serum B12 and folate

4. Serum electrophoresis

5. Serological tests for systemic vasculitis

6. Onconeural antibody profile

7. Neuronal autoimmune panel

Electrodiagnostic studies

1. Nerve conduction studies

2. Sympathetic skin response

Imaging studies

1. Magnetic resonance imaging of the brain

2. Positron emission tomography for underlying malignancy if the cause is not obvious with associated symptoms

Histological studies

1. Intradermal nerve fiber density

2. Fat aspirate with Congo red staining

Abbreviation: HbA_1c, glycated hemoglobin.