What is the diagnostic workup for numbness?

From the Guidelines

The diagnostic workup for numbness should begin with a thorough history and physical examination, including simple clinical tests such as pinprick, temperature sensation, vibration perception, and 10-g monofilament to assess small- and large-fiber function and protective sensation, as recommended by the most recent guidelines 1. The workup for numbness is crucial in determining the underlying cause, which can range from peripheral neuropathy to metabolic disorders like diabetes.

• A thorough history should include questions about the onset, progression, aggravating factors, and accompanying symptoms like weakness or pain.
• The physical examination should assess sensory function, motor strength, reflexes, and coordination.
• Laboratory tests may include complete blood count, comprehensive metabolic panel, vitamin B12, folate, thyroid function, hemoglobin A1c, and ESR/CRP to identify metabolic, inflammatory, or nutritional causes.
• Imaging studies like MRI of the affected area may be necessary to evaluate for structural lesions, compression, or demyelination.
• Electrodiagnostic studies such as electromyography (EMG) and nerve conduction studies (NCS) can help differentiate between peripheral neuropathy, radiculopathy, and other neuromuscular disorders, although they are rarely needed except in atypical or unclear cases 1. The specific workup should be tailored to the clinical presentation, considering that numbness can result from various conditions including peripheral neuropathy, radiculopathy, multiple sclerosis, stroke, or metabolic disorders like diabetes.
• For patients with diabetes, annual assessment for diabetic peripheral neuropathy (DPN) using medical history and simple clinical tests is recommended, as it can predict future risk of complications 1.
• In cases where the diagnosis is unclear or clinical features are atypical, electrophysiological testing or referral to a neurologist may be necessary 1.

From the Research

Diagnostic Workup for Numbness

The diagnostic workup for numbness typically involves a combination of clinical evaluation, laboratory tests, and electrophysiological studies.

• A detailed history of symptoms, family and occupational history, and a neurological as well as general physical exam are essential in the evaluation of peripheral neuropathy 2.
• Pattern recognition of various neuropathies can help to build a differential diagnosis based on the presentation, including acute versus chronic, primary demyelinating versus axonal, hereditary versus acquired, asymmetric versus symmetric, presence of facial palsies, sensory or motor predominant, and presence of prominent autonomic symptoms 2.
• Nerve conduction studies and electromyography (NCS/EMG) is the primary diagnostic tool in the evaluation of patients with large-fiber polyneuropathy 2.
• Laboratory workup includes serum studies and potentially cerebrospinal fluid, genetic studies, immunological markers, and fat pad biopsy for select patients 2.
• Skin biopsy may be used to assess intraepidermal nerve fiber density if small-fiber neuropathy is suspected, and nerve biopsy may be useful in select cases 2.

Importance of History and Physical Examination

• The patient history and physical examination are crucial in selecting relevant diagnostic testing, leading to a timely and accurate diagnosis 3.
• A comprehensive history, physical examination, and judicious laboratory testing are required for the diagnosis of peripheral neuropathy 4.
• The history should include contextual elements such as medical history, social, economic, and psychological background, as well as an assessment of current functional state beyond activities of daily living 5.

Laboratory Tests and Electrophysiological Studies

• Initial laboratory evaluation includes a complete blood count; a comprehensive metabolic profile; fasting blood glucose, vitamin B12, and thyroid-stimulating hormone levels; and serum protein electrophoresis with immunofixation 4.
• Electrophysiological studies, such as NCS/EMG, can help categorize polyneuropathy as primary axonal versus primary demyelinating 2.
• Laboratory tests should be selected specifically according to the suspected type of neuropathy to avoid unnecessary tests and expenses 6.
• Basic screening tests for neuropathies should include a blood cell count, thyroid, renal and liver function tests, blood glucose levels, HbA1c, vitamin-B12, and immunofixation 6.