sensorimotor examination

sensorimotor examination

examination of lower-limb sensory and motor function; i.e. assessment of light touch, pinprick awareness, blunt-sharp discrimination, vibration awareness, monofilament tests, muscle power, Babinski and deep tendon reflexes (see Table 1 and Table 2)
Table 1: Assessment of the motor system of the lower limb
ModalityAssessment
InspectionVisual assessment of the patient's posture, gait, coordination, voluntary and involuntary movements whilst the patient is unaware of being observed
PalpationManual assessment of individual and muscle groups for indications of hypertonia (high resistance to movement followed by a sudden 'give', often indicative of an UMN lesion) or hypotonia (flaccidity, often indicative of LMN and cerebellar lesion)
PowerAssessment of resisted movement (using the MRC grading - see Table 3)
ReflexesPatellar (knee jerk) tendon stretch reflex (quadriceps muscle stretch) and the Achilles (ankle) tendon stretch reflex (gastrocnemius muscle stretch), reinforced as necessary by Jendrassik's manoeuvre. Muscle stretch reflexes are noted as brisk (indicative of an UMN lesion), normal, normal/slow (indicative of underactive thyroid), reduced or absent (indicative of an LMN lesion)
Babinski's reflex (extensor plantar response) is indicative of an UMN lesion
Coordination• Heel-shin test (left heel to slide down right shin and vice versa)
• Fingertip test: where the patient places the index finger on the examiner's finger as this moves apparently at random in front of the patient
Failure to perform in these tests indicates a cerebellar lesion
MovementActive dorsiflexion and plantarflexion, inversion and eversion, and adduction and eversion of the foot against resistance imposed by the examiner:
• Lead pipe rigidity indicates a basal ganglia disorder
• Clasp knife rigidity indicates an extrapyramidal disorder
• Clonus indicates an UMN lesion

UMN, upper motor neurone; LMN, lower motor neurone.

Table 2: Medical Research Council (MRC) muscle-grading scale
GradeMRC grade of muscle strength
0No movement
1Flicker of movement only
2Movement possible when assisted by gravity or gravity is eliminated
3Movement possible against gravity but without imposed resistance
4Weak movement possible against gravity
5Normal movement against gravity and against imposed resistance
Table 3: Sensory evaluation of the lower limb
ModalityType of sensory nerve fibreMeans of evaluation
Light touchMerkel's discs and Meissner's corpuscles of A-beta nerve fibresAwareness of the contact of cotton wool applied to the skin surface
Pinprick painFree, fine nerve endings of A-delta and C fibresAwareness of the weight of the tip of a sterile hypodermic needle on a 2-mL syringe, filled with water, on the skin
Or awareness of the pressure exerted by the metal end of a Neurotip
Or awareness of the pressure applied to the skin by an algometer
Blunt/sharpNeurotip (plastic end) + Neurotip (metal end)
TemperatureFree, fine nerve endings of C nerve fibresAwareness of the contact of cold or heat (e.g. tubes of hot or cold water)
VibrationPacinian corpuscles at the termini of A-beta nerve fibresAwareness of vibration when the instrument is placed against a bony prominence, using:
1. a 128-Hz (middle C) tuning fork (which is appreciated as present or absent)
2. a Rykel-Seiffer 128-Hz tuning fork (the tips of which are weighted and indicate the degree of perceived vibration, in arbitrary units, so that the level of sensory awareness can be recorded; normal sensation = >4)
3. Neuraethesiometer; normal sensation = appreciation of > 23V vibratory stimulus
ProprioceptionThe examiner moves a joint and the patient identifies the direction of movement
Protective painFree, fine nerve endings of A-delta and C fibres10G monofilament (also known as the 5.07 Semmes-Weinstein monofilament)
The normal patient will be able to detect the contact of the tip of the nylon monofilament across the majority of the plantar surface
Ankle jerkGolgi organs in tendons and muscle stretch receptors of A-beta nerve fibresAnkle jerk test, where sudden stretch of the muscle unit, from the contact of the tendon hammer at the tendo Achilles approximately 5cm proximal to its insertion at the calcaneum, excites afferent nerve endings which link within the spinal cord to efferent nerves that pass to the gastrocnemius muscle and cause a brief muscle contraction or twitch

Patients may be unaware of their loss of some or all distal sensation; sensory loss may present as degrees of numbness, paraesthesia or hyperalgesia. The patient should lie relaxed on a couch throughout the assessment, and not watch the tests, in order to avoid visual prompts. Sensory evaluation should be carried out in a systematic manner, with all areas of the foot and all sensory modalities assessed. The distribution of altered sensation (e.g. dermatomal loss; distal loss) is noted on an appropriate form retained within the patient's case notes. Where possible the same clinician should carry out any repeat tests, and repeat tests, e.g. every 6-12 months should be made at the same time of day as the original assessment, due to the diurnal variation in sensory awareness.