Lower Limb Motor Assessment: OSCE Procedure Guide

The sensory-motor-reflex approach localizes neurological lesions: radiculopathy shows radicular pain with precipitating/relieving factors and root-specific reflex changes; plexopathy shows pain in plexus location radiating along multiple nerves without clear precipitants; peripheral neuropathy shows symmetrical sensory-motor involvement without root-specific patterns. This systematic approach distinguishes between these entities, guiding appropriate diagnostic workup and treatment strategies.

Spinal cord involvement produces bilateral motor and sensory symptoms. Nerve root involvement causes shooting pain on one side (radicular pain). Neuropathy causes distal weakness. The presence of both motor and sensory symptoms with bilateral involvement strongly suggests spinal cord pathology. The pattern of sensory involvement (pain and temperature crossing over) is characteristic of spinal cord lesions.

This video teaches medical students how to localize peripheral nervous system lesions by understanding the motor and sensory functions of major nerves in the arm (ulnar, median, musculocutaneous, radial, axillary) and leg (femoral, obturator, sciatic with tibial and common fibular branches), distinguishing nerve injuries from radiculopathies through characteristic patterns of weakness, sensory loss, and reflex changes. For example, ulnar neuropathy causes weakness in finger adduction and thumb adduction with sensory loss in the ulnar distribution, while C8 radiculopathy presents with similar motor deficits but includes sensory loss in the medial forearm and radicular pain. Similarly, femoral neuropathy causes knee extension weakness and thigh sensation loss, whereas L4 radiculopathy may also affect foot dorsiflexion and inversion. Understanding these differences is essential for proper diagnosis and management of peripheral nerve disorders.

Peripheral neuropathy patterns: glove and stocking distribution (most common), diabetic neuropathy (most common cause). Spinal cord lesions can be localized based on sensory level, motor level, and autonomic level. The pattern of sensory loss (dissociated sensory loss, Brown-Séquard syndrome) helps localize the lesion. The key is to identify which tracts are affected.

Radiculopathy results from nerve root compression and presents with characteristic neurological deficits. Radicular pain typically affects regions below the knee, while somatic pain from musculoskeletal compression localizes to the gluteal or thigh regions. Clinical assessment includes myotome testing for motor function—for example, L5 radiculopathy affects tibialis anterior (great toe extension). Sensory evaluation examines dermatome distribution for decreased sensation. Reflex testing assesses patellar (L4) and Achilles (S1) reflexes, which may be diminished or absent. These neurological signs help localize the level of nerve root involvement and distinguish radicular from somatic causes.

Coordination testing includes finger-to-nose (upper extremity) and heel-to-shin (lower extremity). For finger-to-nose, hold your hand far enough that the patient must fully extend to reach, looking for side-to-side weaving and difficulty hitting the stationary target in cerebellar ataxia. For heel-to-shin, slide the heel up and down the tibia, watching for side-to-side swaying on the shin. Gait assessment includes normal walking and tandem (heel-to-toe) walking. The Romberg test (standing with eyes closed) tests balance by removing visual input, revealing problems with vestibular or proprioceptive systems. A positive Romberg indicates deficit in one of these systems.

The Romberg test assesses balance and proprioception by having the patient stand with feet together and arms out, first with eyes open and then closed. Negative results indicate no significant neurological impairment. Coordination tests include finger-to-nose testing (moving finger to nose and then to examiner's finger) and heel-to-shin testing (moving heel along shin).

The heel-to-shin test evaluates coordination: (1) The patient places their heel on their opposite knee, (2) The examiner observes accuracy and smoothness of movement, (3) Normal findings: The heel touches the knee directly and moves in a straight line, (4) Abnormal findings: Overshooting, undershooting, or irregular paths indicate cerebellar dysfunction. The Romberg test evaluates sensory ataxia: (1) The patient stands with feet together and closes their eyes, (2) The examiner observes for 60 seconds, (3) Normal findings: The patient maintains balance, (4) Abnormal findings: Swaying, staggering, or falling indicate sensory ataxia or vestibular dysfunction.

This segment covers lower extremity coordination and balance tests: heel-to-shin test (sliding heel down opposite shin), rebound test (resisting arm movements), Romberg test (standing with feet together, eyes open then closed), Romberg test with feet apart, and tandem gait test (walking with feet one in front of the other). These tests evaluate lower extremity coordination, balance, and proprioception. The examiner stands behind or beside the patient to prevent falls. Results are documented on the medical chart.

The Romberg test is controlled by input from the eyes, vestibular system, and proprioception. To perform, the patient stands with feet together and removes their shoes. The physician removes visual input by closing the patient's eyes and observes whether the patient maintains balance or sways. If the patient sways or falls, this indicates dysfunction in the vestibular system, proprioception, or visual system. After the Romberg test, observe the patient's gait with eyes open. Watch whether the gait is straight or if there is deviation to one side. This helps identify vestibular or cerebellar dysfunction.

Upper motor neuron (UMN) findings include hyperreflexia, hypertonia, Babinski sign, and clonus. Lower motor neuron (LMN) findings include hypotonia, hyporeflexia, fasciculations, and muscle wasting. ALS is characterized by the combination of both UMN and LMN findings, which is a critical diagnostic feature. The presence of both types of findings in the same patient strongly suggests ALS rather than other neurological conditions.

Upper motor neuron lesions can be identified through specific neurological signs including hyperreflexia (exaggerated reflexes), clonus (sustained rhythmic muscle contractions), and a positive Hoffman's sign (index finger flexion when the middle finger is flicked); these findings collectively indicate damage to the central nervous system and warrant referral to a neurologist or physiatrist for further evaluation and diagnostic testing such as MRI.

Hyperreflexia in young patients requires differential diagnosis including: (1) physiological hyperreflexia without underlying pathology, (2) drug-induced causes (serotonin syndrome), (3) motor neuron disease, (4) multiple sclerosis, and (5) other neurological conditions. The patient's bilateral symmetric hyperreflexia without other neurological deficits makes motor neuron disease less likely.

Four key clinical signs indicate upper motor neuron dysfunction: (1) Hyperreflexia - exaggerated muscle stretch reflexes due to supersensitive lower motor neurons; (2) Clonus - rhythmic antagonist muscle contractions triggered by reciprocal reflex activation; (3) Hypertonia - increased muscle resistance during passive movement; (4) Babinski sign - extensor plantar response where toes extend upward when scraping the foot sole. These signs contrast with lower motor neuron signs like hyporeflexia and hypotonia, helping clinicians distinguish between upper and lower motor neuron lesions.

Upper motor neuron lesions show hyperreflexia, clonus, Babinski sign, increased tone (spasticity - velocity-dependent), minimal atrophy. Lower motor neuron lesions show areflexia, flaccidity, significant atrophy, and fasciculations. Fasciculations alone are benign but with weakness indicate pathology. Spasticity is velocity-dependent (catch on quick movement); rigidity is non-velocity-dependent (seen in Parkinson's). Paratonia is resistance to passive movement from frontal lobe dysfunction (Alzheimer's).