sensory exam of the lower limbs

Question 1

first thing you do

Answer 1

W -­‐‑ Wash your hands. I -­‐‑ Introduce yourself to the patient P -­‐‑ Permission. Explain that you wish to perform an examination of their legs and obtain consent for the examination. Pain. Ask the patient if they are in any pain and to tell you if they experience any during the examination. E -­‐‑ Expose the necessary parts of the patient. Ideally the patient should be undressed from the waist down (excluding underwear) taking care to ensure the patient is not cold or unnecessarily embarrassed. R -­‐‑ Repostition the patient. In this examination the patient should be supine.

Question 2

5 modalities to test

Answer 2

There are five modalities of the sensory system; light touch, pain, temperature, proprioception and vibration. Symptoms of an alteration in sensation include numbness, pins and needles and pain. Start each examination by asking the patient if they have any areas of altered sensation-­‐‑ if in an OSCE, ask the examiner if this is okay as this is borderline history taking. The stimuli being tested is demonstrated to the patient with their eyes open before being tested with their eyes closed. Proprioception and vibration are demonstrated on the patient’s feet; light touch, pain and temperature are demonstrated on the patient’s torso or arm-­‐‑the levels are usually NOT the same even for same pathway so don’t be surprised-­‐‑classically joint perception may only be affected to digits but vibration much further up limb). Light touch, pain and temperature are then examined in all the dermatomes. (see fig 4)

Question 3

Light Touch

Answer 3

Use a wisp of cotton wool or monofilament, if cotton wool is used do not drag it over the skin but apply it to a single point. Demonstrate the sensation to the patient-­‐‑use their torso with their eyes open. Then ask them to close their eyes and to say ‘yes’ when they can feel the sensation of being touched with whichever object you are using (just feeling “something” is not necessarily normal-­‐‑ they should be able to identify it). Examine each dermatome in a systematic manner (this can be done comparing legs or testing each leg separately). If an area of abnormality is found map out the extent of the problem-­‐‑ is it dermatomal or glove and stocking distribution?

Question 4

Pain

Answer 4

(DON’T say PAIN to the patient-­‐‑say PINPRICK SENSATION!!) This is examined using a neurological pin (Neurotip). Needles or cannulae should not be used as these can puncture the skin. The examination routine is the same as that used for light touch and the patient should be able to feel the stimulus as sharp. (It is often done at the same time getting the patient to differentiate between the stimuli). Pain (and temperature) is conveyed by the spinothalamic tract.

Question 5

Temperature

Answer 5

This is not generally performed in a routine examination however it can be examined in the same way as light touch. As both hot and cold are carried on the same fibres it is sufficient to test one, due to lack of available equipment this is normally cold using the metal of the tuning fork.

Question 6

Proprioception

Answer 6

This is examined by testing the joint position sense in the big toe. First isolate the joint by holding it apart from the other toes. Hold the distal phalanx of the patient’s large toe at the sides to avoid giving information from pressure. Demonstrate the movements of ‘up’ and ‘down’ to the patient. Ask the patient to close their eyes and to say whether the movement is up or down. Proprioception can also be assessed by Romberg’s test: ask the patient to stand with feet together with both eyes open (be in a position in which to catch patient if required-­‐‑ ie hand behind & in front of the patient). Then ask the patient to close their eyes. If they are more unsteady with their eyes closed this is a sign of difficulty with proprioception. Remember that proprioception (and vibrational sense) is conveyed by the dorsal column/medial lemniscal pathway.

Question 7

Vibration

Answer 7

Use a 128 Hz tuning fork. Demonstrate the sensation on the sternum. To ensure that you are testing vibration rather than sensation ask the patient first ‘if they feel buzzing sensation’. If they answer yes; ask them to tell you when ‘it stops’. Vibration is tested on bony prominences, initially on the medial aspect of the big toe. If vibration is absent here then the tuning fork should be moved proximally to establish the level at which it can be appreciated. Start at a boney part of the toes, the medial or lateral malleolus, then the upper part of the tibia, then the iliac crests.

Question 8

after vibration?

Answer 8

Finally explain to patient that you have finished your examination, thank them for their cooperation and help them to get dressed.