🩺 Peripheral Neurological Examination

The peripheral neurological examination is a systematic assessment of the motor and sensory functions of the limbs to localise lesions within the nervous system. It involves an ordered evaluation of muscle bulk, tone, power, reflexes, sensation (light touch, pain, vibration, proprioception), and coordination. This skill is vital for distinguishing between upper and lower motor neuron lesions and identifying peripheral nerve or root pathologies. Success depends on a methodical approach and the ability to correlate physical findings with neuro-anatomical structures.

This examination is indicated for any patient presenting with motor symptoms such as weakness, clumsiness, or muscle wasting, or sensory symptoms like numbness, tingling (paresthesia), or neuropathic pain. It is a core component of the assessment for suspected stroke, multiple sclerosis, peripheral neuropathies (e.g., diabetic or B12 deficiency), and radiculopathies (e.g., sciatica). It is also essential in the routine monitoring of chronic neurological conditions and the acute assessment of potential spinal cord compression or cauda equina syndrome. Any unexplained fall, particularly in the elderly, warrants a full peripheral neurological screen.

There are no absolute contraindications to a peripheral neurological examination, but procedures should be modified in the presence of acute trauma, such as suspected limb fractures or severe skin integrity issues. In patients with suspected acute spinal cord injury or cauda equina syndrome, any movement of the limbs must be performed with extreme caution and in accordance with spinal immobilisation protocols. Sensory testing using a neuro-tip should be avoided on areas of broken skin or active infection. Relative contraindications include patients who are unable to follow commands due to severe cognitive impairment or decreased consciousness.

The required equipment includes a tendon hammer (Queen Square or similar) for eliciting deep tendon reflexes and a 'Neuro-tip' or disposable sterile pin for assessing sharp-touch sensation. A 128Hz tuning fork is essential for assessing vibration sense; higher frequencies are inappropriate for this purpose. Cotton wool is used for light touch (dorsal columns/spinothalamic), and a neuro-wheel or specific objects may be used for proprioception. A stethoscope may occasionally be used to auscultate for bruits in specific vascular-neurological contexts, and a torch may assist in visualising muscle bulk.

The procedure begins with a general inspection for muscle bulk, involuntary movements, and posture. In the upper limbs, assess tone at the wrist and elbow, followed by power testing of major muscle groups (shoulder abduction through to finger abduction). Reflexes (biceps, supinator, and triceps) are performed with a relaxed limb. Sensory testing includes light touch, pinprick, vibration (at the DIP joint of the index finger), and proprioception. In the lower limbs, inspection is followed by tone (leg roll and knee flick), power (hip flexion through to hallux extension), and reflexes (knee and ankle). The plantar response is elicited by stroking the lateral aspect of the sole. Assessment of coordination (finger-nose and heel-to-shin) and gait completes the exam.

Interpretation follows a 'site of the lesion' logic: upper motor neuron (UMN) vs. lower motor neuron (LMN). UMN lesions (e.g., stroke, MS) typically present with hypertonia (spasticity), hyperreflexia, and upgoing plantars (Babinski sign), with weakness usually affecting extensors in the arms and flexors in the legs. LMN lesions (e.g., peripheral nerve palsy, radiculopathy) present with hypotonia, hyporeflexia or areflexia, muscle wasting, and fasciculations. Sensory patterns also aid localisation: a 'glove and stocking' distribution suggests peripheral neuropathy, while a specific dermatomal loss suggests nerve root involvement. Findings must be correlated with gait and coordination to differentiate between pyramidal, extrapyramidal, and cerebellar pathology.

Common pitfalls include failing to test for 'sacral sparing' if a spinal cord lesion is suspected or neglecting to check the back for surgical scars or spinal tenderness. Students often perform sensory testing too quickly, failing to allow the patient time to respond, or they do not compare left to right systematically. Forgetting to test coordination (pseudoathetosis or finger-nose) can lead to missing cerebellar or posterior column pathology. In the lower limbs, failing to adequately expose the patient may result in missing subtle fasciculations or muscle wasting in the hamstrings or calves.

Always start with an inspection from the end of the bed, looking for wasting, fasciculations, or tremors. When testing power, ensure you are testing across a single joint and stabilising the proximal limb to prevent compensation. For sensation, always establish a 'reference point' (e.g., the sternum) so the patient knows what the stimulus should feel like. In reflexes, if they are difficult to elicit, use reinforcement manoeuvres like Clenching teeth (Jendrassik) for lower limbs. Ensure the patient is fully relaxed during tone assessment, as guarding can mimic spasticity or rigidity.

Aligned with the MLA 'Clinical Assessment' theme; students must demonstrate a systematic approach (Tone, Power, Reflexes, Sensation, Coordination). Awareness of the Dermatome map (C5-T1 and L2-S1) and the specific nerve roots for reflexes (C5/6 Biceps, C7/8 Triceps, L3/4 Knee, S1/2 Ankle) is frequently tested. Candidates should be prepared to discuss the clinical significance of a positive Babinski reflex and the difference between cerebellar ataxia and sensory ataxia. Documentation should clearly state if the findings are focal, symmetrical, or follow a specific neuro-anatomical distribution.