Neurological Examination of the Arms : General stuff

We carry out neuro exams of the arms for two main reasons : 1. to find the site of the lesion, 2. to form a list of differential diagnoses.

Types of lesions - they may be MOTOR / SENSORY / MIXED

Remember one motor neuron pathway- has two components - the Upper motor neurone [from cells in the precentral gyrus of the frontal cortex, through the internal capsule, brainstem, cord, anterior horn cells in the cord] and the lower motor neurone [nerve roots, plexi, peripheral nerves] .

UPPER MOTOR NEURONE lesion (affects groups of muscles not individual muscles):

• no fasciculations



• wasting after some times



• increased tone (spasticity - arm flexors, leg extensors ; manifested as resistance to passive movment that can suddenly be overcome - 'clasp-knife' feel)



• weakness



• increased reflexes



• upgoing plantars(+babinski) +/- clonus (rapidly dorsiflexing the foot; < or =" 3">

LOWER MOTOR NEURONE lesion:

• yes fasciculations (spontaneous involuntary twitching)



• wasting



• decreased tone ''HYPOTONICITY''/Flaccidity (soft and floppy, little resistance to passive stretch)



• weakness



• decreased reflexes/reduced or absent

MYOTOMES

Shoulder joint: c5 abduction and lateral rotation; C7 abduction and medial rotation

Elbow joint: C5-6: flexion; C7-8: extension

Wrist joint: C6-7: Flexion/extension

Fingers: C7-8: Flexion/Extension; T1: Abduction/Adduction (small muscles of the hand)

POWER GRADES:

0;complete paralysis

1; a flicker of movement only

2;able to move when gravity is eliminated

3;just able to move against gravity

4;able to move against gravity with some resistance

5; normal



REFLEXES

Biceps jerk : C5,6

Triceps Jerk: C7,8

Supinator jerk; C6,7



Recording reflexes:



+ hyporeflexia; +/- present with reinforcement; ++ normal; +++hypereflexia



Sensory:



dermatomal

peripheral



sensory modalities:

pain&temp (spinothalamic) (spinster...spino pinprick)

Light touch, vibration, proprioception (dorsal columns)

Myotome effect:
C3,4 and 5 supply the diaphragm (the large muscle between the chest and the belly that we use to breath).
C5 also supplies the shoulder muscles and the muscle that we use to bend our elbow .
C6 is for bending the wrist back.
C7 is for straightening the elbow.
C8 bends the fingers.
T1 spreads the fingers.
T1 –T12 supplies the chest wall & abdominal muscles.
L2 bends the hip.
L3 straightens the knee.
L4 pulls the foot up.
L5 wiggles the toes.
S1 pulls the foot down.
S3,4 and 5 supply the bladder. bowel and sex organs and the anal and other pelvic muscles.

[http://www.apparelyzed.com/myo-dermatomes.html
can get a relatively okay dermatome map here]

http://en.wikipedia.org/wiki/Image:Dermatoms.svg