This test using a wisp of cotton wool in area of total loss of sensation. In polyneuropathy ,sensory loss is symmetrical and follow a characteristic stocking and glove distribution.
In Polyneuropathy ,Two point discriminationΒ help to testΒ the ability to discriminate two blunt points when simultaneously applied to the finger, 5mm apart .
Place a vibrating tunning fork (usually 128 c/s ) on a bony prominence, e.g. radius. Ask the patient to indicate when the vibration, if felt, ceases. If impaired, move more proximally and repeat . Vibration testing is of value in the early detection of demyelinating disease and peripheral neuropathy, but otherwise is of limited benefit.
Hold the sides of the patient’s finger or thumb and demonstrate ‘up and down ‘ movements.
Temprature testing seldom provides any additional information. If required, use a cold object or hot and cold test tubes.
Pin prick with a sterile pin provides a simple method of testing this important modality. Firstly, Check that the patient detects the pin as ‘sharp’,.i.e. painful, then rapidly test each dermatome in turn.
Joint position impairment , sensory ataxia is evident. Romberg’s test is positive.Neuropathic burns / ulcers or joint may be present .
Evident is axonal but absent in demyelinating neuropathies .Oedema of immobile limbs may mask wasting. The 1st dorsal interosseous muscle in the upper limbs and extensor digitorum brevis in the lower limbs are muscle groups. Look for fasciculations – irregular twitches of groups of muscle fibres due to diseased anterior horn cells , these may be induced by exercise or muscle percussion .
Weakness is proportional to the number of affected motor neurons. It develop suddenly or slowly and is generally symmetrical , usually starting distally in the lower limbs and spreading to upper limbs in a similar manner before ascending into proximal muscle groups . This pattern of progression is supposedly due to the ‘dying back ‘ of axons towards their nerve cells – the longest being the most vulnerable. Some neuropthies, e.g. Guillain -Barre, chronic inflammory demyelinating polyneuropathy, may affect proximal muscle groups first.
In sever neuropathies , truncal and respiratory muscle involvement occurs. Respiratory muscle weakness may result in death.
The tendon reflex depends on:
Reflexes commonly tested :
BICEPS REFLEX
Ensure patient’s arm is relaxed and slightly flexed. Palpate the biceps tendon with the thumb and strike with tendon hammer . Look for elbow flexion and biceps contraction .
SUPINATOR REFLEXΒ
Strike the lower end of the radius with the hammer and watch for elbow and finger flexion.
TRICEPS REFLEX
Strike the patient’s elbow a few inches above the olecranon process. Look for elow extension and triceps contration.
KNEE REFLEX
Ensure that the patient’s leg is relaxed by resting it over examiner’s arm or by hanging it over the edge of the bed. Tap the patellar tendon with the hammer and observe quadriceps contration Note impairment or exaggeration.Β
ANKLE REFLEXΒ
Externally rotate the patient’s leg. Hold the foot in slight dorsiflexion. Ensure the foot is relaxed by palpating the tendon of tibialis anterior. If this is taut, then no ankl jerk will be elicited.Β
Tap the Achillies tendon and watch for calf muscle contration and plantarflexion.Β
Neurology and neurosurgery illustrated by Kenneth W Lindsay ,Page 430-444
Clinical Methods: The History, Physical, and Laboratory Examinations. 3rd edition. Chapter – 67 Sensation.
Washington University in St .Louis , Neurological examination.
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