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During any examination in an OSCE it is important to understand the pathology and reasoning behind each of the signs and symptoms elicited, even if the patient being examined is ‘normal’. This article explains how to perform a lower limb neurological examination and the key findings you should look for, showing you what each sign means and what conditions it may indicate.
The central aim of this examination is to work out where a problem lies within the nervous system. The most useful distinction to keep in mind throughout is between an upper motor neurone (UMN) lesion (in the brain or spinal cord) and a lower motor neurone (LMN) lesion (in the anterior horn cell, nerve root, plexus or peripheral nerve). Almost every sign you elicit helps to place the lesion into one of these patterns.
Contents
Introduction
Wash your hands and don personal protective equipment if appropriate.
Introduce yourself to the patient and ensure to mention your grade e.g. 3rd year medical student/junior doctor/consultant.
Confirm the patient’s details taking 3 points of identification usually; full name, date of birth and NHS/hospital number.
Obtain consent for the examination, ensuring to explain what the examination will entail. A useful explanation is that you would like to look at how the nerves and muscles of the legs are working, which will involve watching them walk, moving their legs, tapping their knees and ankles, and testing sensation.
Ask the patient about any pain, particularly in the back, hips or legs, before you begin moving the limbs.
Expose the patient’s lower limbs fully (ideally down to underwear) so that muscle bulk and any abnormal movements can be seen, and position them lying on the bed with the head supported and the legs flat.
Before you start, gather your equipment: a tendon hammer, a 128 Hz tuning fork (for vibration sense), a neuro-pin (for pin-prick) and cotton wool (for light touch). Having everything to hand keeps the examination slick and shows the examiner you know what each modality requires.
General Inspection
Begin by standing back and observing the patient and the area around the bed. Look at the patient’s general comfort and posture, and note any mobility aids such as walking sticks, a frame, a wheelchair or ankle-foot orthoses, which give immediate clues about the degree of disability and its cause.
Look around the bedside for objects of relevance, such as catheters (which may accompany a spinal cord lesion), prescriptions, or adaptations suggesting a chronic neurological condition.
Inspect the legs themselves for muscle wasting, fasciculations, tremor, abnormal posturing and scars.
- Muscle wasting suggests a lower motor neurone lesion or simple disuse atrophy. Asymmetry between the two legs is particularly informative.
- Fasciculations are fine, flickering, involuntary twitches of muscle fibres seen under the skin. They result from spontaneous motor-unit discharge and may be benign in isolation. Associated weakness, wasting or reflex abnormalities suggest a lower motor neurone disorder; progressive weakness warrants assessment.
- Scars over the spine or limbs may indicate previous spinal surgery, joint replacement or nerve repair, all of which can explain neurological signs.
- Abnormal posturing of a limb, such as a leg held extended and internally rotated, can point to a long-standing UMN lesion such as a previous stroke.
- Tremor or other involuntary movements at rest may suggest a Parkinsonian or other movement disorder.
- Pseudoathetosis describes slow, writhing movements of the toes when the patient cannot see the limb, caused by loss of proprioception rather than a primary movement disorder; it points back to the dorsal columns.
It is also worth glancing at the patient’s footwear if it is to hand: uneven wear at the toe can betray a chronic foot drop from scuffing the ground.
Gait
Assessing gait is one of the most valuable parts of the examination because it integrates motor power, coordination, proprioception and balance all at once. If it is safe to do so, ask the patient to walk a few metres, turn, and walk back, staying close in case they are unsteady.
Observe the symmetry, stride length, arm swing, the turn, and whether the patient is steady. Several characteristic patterns may emerge:
- Hemiplegic gait – one leg is held stiff and extended and is swung outwards in an arc (circumduction) with each step. This reflects a UMN lesion on one side and is classically seen after a stroke.
- High-stepping gait – the patient lifts the foot high to avoid catching the toes on the ground because of foot drop (weak ankle dorsiflexion). This indicates a problem with the common peroneal nerve, the L5 root, or a peripheral neuropathy.
- Ataxic gait – a broad-based, unsteady, lurching walk. A cerebellar cause produces a wide stance that does not improve with vision, whereas a sensory (proprioceptive) ataxia worsens markedly when the eyes are closed.
- Parkinsonian gait – small shuffling steps, reduced arm swing, a stooped posture and difficulty initiating and turning, seen in Parkinson’s disease.
- Waddling gait – the pelvis drops on alternate sides, seen with proximal myopathy.
Where appropriate you may also ask the patient to walk heel-to-toe (tandem gait), which exaggerates a cerebellar ataxia, and to walk on their toes and heels to screen plantarflexion (S1) and dorsiflexion (L4/L5) respectively.
Romberg’s Test
Romberg’s test assesses dependence on visual input for standing balance. A positive result may reflect impaired proprioception or, less commonly, severe bilateral vestibular loss; it is not a specific test of cerebellar function. Ask the patient to stand with their feet together and arms by their sides, and stand close by ready to catch them. Once they are stable with their eyes open, ask them to close their eyes.
Maintaining balance relies on three inputs: vision, proprioception and the vestibular system. With the eyes open, the patient can compensate for poor proprioception using vision. When the eyes close, that compensation is removed, so a patient with impaired proprioception (for example from dorsal column disease, peripheral neuropathy or B12 deficiency) becomes markedly more unsteady or falls – a positive test.
Romberg’s test is often wrongly thought to assess the cerebellum. Cerebellar ataxia usually causes difficulty standing steadily even with the eyes open. Becoming markedly less steady on eye closure may indicate impaired proprioception or severe bilateral vestibular loss. Test joint position sense and assess vestibular function to distinguish these causes rather than assigning the result to proprioception alone.
Tone
Tone is the resistance felt in a muscle when it is passively moved. Ask the patient to relax and ‘let the leg go floppy’, then assess tone by performing a leg roll (rolling the relaxed thigh from side to side and watching the foot flop) and a leg lift (briskly lifting the knee off the bed and watching whether the heel stays in contact or flies up).
- Increased tone (hypertonia) indicates a UMN lesion. Spasticity is velocity-dependent, being more pronounced with rapid movement, and is typical of UMN lesions such as stroke or spinal cord disease. Rigidity (which includes the ‘lead-pipe’ and ‘cog-wheel’ varieties) is present throughout the range of movement and is associated with Parkinson’s disease and other extrapyramidal disorders.
- Reduced tone (hypotonia) can be seen with LMN lesions and in the acute phase of a UMN lesion (‘spinal shock’), though it is a subtle sign.
Next assess for ankle clonus. With the leg relaxed and slightly externally rotated and the knee bent, briskly dorsiflex the foot and hold it in dorsiflexion. Clonus is felt as a series of involuntary, rhythmic beats of plantarflexion and dorsiflexion. A few beats can be normal, but sustained clonus (more than around five beats) is abnormal and is a sign of a UMN lesion.
Quiz
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