Peripheral neuropathy describes a condition resulting from damage to the peripheral nervous system, the vast network of nerves outside the brain and spinal cord. These nerves are responsible for relaying information between the central nervous system and the rest of the body, governing sensation, movement, and organ function. The physical examination is an indispensable first step in diagnosis, serving to confirm the patient’s reported symptoms and establish a baseline of nerve function. The primary goal of this evaluation is to map the pattern of nerve damage, which often follows a length-dependent distribution. This means the longest nerves—those extending to the feet—are affected first, guiding subsequent diagnostic testing.
Identifying Sensory Deficits
Sensory symptoms, such as numbness, tingling, burning, or pain, are often the earliest and most common complaints in neuropathy. A detailed sensory examination is conducted to map these deficits.
One telltale sign is the “stocking-glove” pattern, where sensory loss is symmetrical and affects the feet and lower legs first, then progresses to the hands, resembling the areas covered by stockings and gloves. This distribution reflects the length-dependent nature of nerve fiber damage.
The evaluation of light touch and pain sensation is performed using a cotton swab and a pinprick, respectively, to identify areas of diminished feeling (hypoesthesia) or complete loss of feeling (anesthesia). A nylon monofilament is frequently used to apply a standardized pressure, which helps to objectively quantify the loss of protective sensation, particularly in the feet. Abnormal sensations, such as allodynia (painful response to a non-painful stimulus) or hyperalgesia, also indicate nerve fiber dysfunction.
Testing for vibration sense is often the most sensitive indicator of large nerve fiber damage and is usually the first sensation to be lost. A 128-Hz tuning fork is applied to a bony prominence, such as the big toe or ankle, and the patient reports when the vibration stops. A reduced or absent perception of this vibration is a significant finding.
Proprioception, the sense of joint position, is assessed by gently moving the patient’s toe or finger up or down and asking the patient to identify the direction of movement with their eyes closed. Loss of proprioception indicates damage to the large, heavily myelinated sensory fibers and can profoundly affect balance. Temperature discrimination is tested with warm and cool objects to check the function of the small, unmyelinated nerve fibers responsible for pain and temperature perception.
Evaluating Motor Function and Muscle Integrity
The motor component of the physical examination focuses on the ability of the peripheral nerves to control muscle movement. The physician systematically assesses muscle strength against resistance, often using a standardized grading system like the Medical Research Council (MRC) scale to document the degree of weakness. Patterns of weakness, such as a foot drop or a wrist drop, can indicate specific nerve involvement.
Muscle atrophy, or wasting, is a visible sign of chronic motor nerve damage, as the muscle fibers shrink without the necessary nerve stimulation. This is frequently noticeable in the small muscles of the hands and feet. The physician also visually inspects for fasciculations, which are small, involuntary muscle twitches that appear as ripples under the skin and indicate irritation or damage to the motor nerve cell.
The examination includes observation of trophic changes, which are alterations in the skin, hair, and nails that accompany severe nerve damage. These changes, such as excessively dry skin, brittle nails, or hair loss in the affected limb, occur because of the loss of nerve-mediated control over blood flow and sweat gland function.
Assessing Deep Tendon Reflexes and Coordination
The neurological exam involves evaluating deep tendon reflexes (DTRs) and coordination. Using a reflex hammer, the physician tests DTRs, such as the Achilles (ankle jerk) and patellar (knee jerk) reflexes, which are automatic, involuntary muscle contractions in response to the stretch of a tendon.
A hallmark finding in peripheral neuropathy is diminished or absent reflexes (hyporeflexia or areflexia), particularly in the distal extremities. The Achilles reflex is often the first to be lost, and its absence is a strong indicator of peripheral nerve damage. This finding helps differentiate peripheral nerve issues from central nervous system problems, where reflexes are often hyperactive.
Gait assessment is performed by observing the patient walk, which can reveal an unsteady or broad-based gait due to proprioceptive loss. A high-stepping or “steppage” gait may be observed if the patient has significant weakness in the muscles that lift the foot.
Coordination and balance are further tested using the Romberg test, where the patient stands with feet together, first with eyes open and then with eyes closed. A positive Romberg sign, characterized by increased unsteadiness when the eyes are closed, strongly suggests a loss of proprioception.