Examination of the peripheral nervous system

The motor system
· Inspection & palpation of muscle groups
· Assessment of tone
· Testing of power
· Elicitation of deep tendon reflexes & plantar responses
· Testing of co-ordination

Inspection & palpation
· Normal variety in muscle bulk & power
· Lower limb musculature symmetrical
· Upper limb musculature more developed in dominant side
· Muscle wasting - Assess distribution. Focal or diffuse. Proximal or distal. Involving peripheral nerve or spinal segment.
· Fasiculations - subcutaneous twitches overlying muscle bellies when muscles are at rest. LMN disease. Brief contraction of single motor units.
· Myoclonus - Sudden, shock-like muscle contraction involving one or more muscle of a whole limb. Focal or diffuse and occur singly or repetitively.
· Choreiform movements - irregular, jerky, semipurposeful. Huntington’s chorea.
· Tics
· Tremor
· Dystonic movements - slow & writhing. Often lead to sustained abnormal contracture & limb posturing
· Pronator drift – ask patient to close eyes and hold out arms with hands supinated. If UMN lesion is present hand will drift into pronation..


Tone
· Ask patient to relax and ‘go floppy’
· Passively flex & extend each joint in turn. Start slowly then more rapidly.
· Upper limbs - test shoulder, elbow joint & wrist joint
· Lower limb - Internal & external rotation of resting leg. Briskly raise knee off leg and watch to see if ankle is also raised.
· Knee clonus - Push patella sharply towards foot and palpate for further jerks.
· Ankle clonus - Support flexed knee with one hand in popliteal fossa so ankle gently rests on the bed. Using other had briskly dorsiflex the foot and sustain the pressure
· Sustained clonus is a sign of UMN damage

Power
· Power is relative to the patient
· Examine muscle groups against contralateral group
· Isometric testing - Patient contracts muscle group & maintains position as examiner tries to overpower group being tested.
· Isotonic testing - Ask patient to put a joint through a range of movement while trying to stop the movement

MRC scale for muscle power
0 - No muscle contraction visible
1 - Muscle contraction visible, but no movement of joint
2 - Joint movement when effect of gravity eliminated
3- Movement sufficient to overcome effect of gravity
4- Movement overcomes gravity plus added resistance
5- Normal power

Deep tendon reflexes
· Biceps jerk - C5, C6
· Triceps jerk - C6, C7
· Supinator jerk - C5, C6
· Knee jerk - L3,L4. Legs must not be in contact
· Ankle jerk - S1
· If difficult have patient grit teeth or pull against hands

Plantar response L5/S1
· Normal - normal plantar flexion of big toe and other toes.
· Positive Babinski sign - dorsiflexion

Clonus
· Rhythmical repetitive plantar flexion and dorsiflexion
· Loss of supraspinal inhibition
· Sharp muscle stretching causing oscillation within circuit of the reflex arc
· Normal – a few beats
· Pathology – asymmetrical or sustained

Hoffman reflex
· Lesion at level of C5/6 – supinator jerk
· Inversion of supinator jerk – flexion of the fingers
· Supinator/biceps often lost
· Can be elicited by ‘flicking’ one finger – all other fingers should flex
· Similar to Babinski

Co-ordination
· Finger-nose test
· Rapid alternating movements
· Heel shin test.

The sensory system
· Proprioception
· Light touch
· Pin prick
· Vibration
· Temperature
· Two point discrimination
· Aim to determine if any modalities are impaired and to determine the site of any lesion

Examination system
· Touch - cotton wool, tissue paper or light touch
· Pain - pin
· Deep pain - squeeze muscle bellies
· Temperature - cool object - tuning fork
· Joint position sense - Start distal. Show patients movements and name them. Close eyes. Avoid guessing.
· Vibration sense - tuning fork
· Two point discrimination