Practical CNS

Sensory System ExaminationMotor System ExaminationExamination of Coordination (Cerebellum)

Sensory System Examination

Sensation Tool used

Receptor Tract

Touch:-Crude-Fine Touch:-Tactile localization-Tactile discrimination-Stereognosis

-Cotton wool/brush

-2 marker pens

-compass

- Familiar objects

-Cutaneous mechanoreceptors.

-cutaneous mechano.-Cutaneous mechano.-Cutaneous mechano.

-Anterior spinothalamic tract

- Dorsal Column- medial lemniscal system.

Pain Pin Free nerve endings -Lateral spinothalamic tract

Proprioception:-Sense of position-Sense of movement

Joint of patient Proprioceptors - Dorsal column- medial lemniscal system

Temperature Two test tubes Free nerve endings -Lateral spinothalamic tract

Stereognosis: The ability to identify common objects by feeling them, with eyes closed, it is a complex sensation based on the synthesis of many sensations, such as touch, pressure, temperature..etc.

Proprioception: Arise from stimulation of receptors within

the body tissues and include sense of position and movement.

Static proprioception: awareness of location of different parts of the body (body image).

Kinesthetic proprioception: perception of the rate of movement of different parts of the body.

Motor System Examination

1. Inspection of muscle state

Inspection means using one’s vision.The abnormal muscle states include:

Atrophy.Hypertrophy.

2. Muscle tone (passive movement)

Here you have to notice resistance:Normotonia Hypotonia: e.g. poliomyelitis and spinal muscular

atrophy.

Hypertonia :Rigidity (cog-wheel) : e.g. Parkinson disease.Spasticity (clasp- knife) : e.g. Upper motor neuron

lesions.

3. Muscle power (active movement).

4. Superficial reflexes :Planter reflexes.Abdominal reflexes.Cremasteric reflexes.

The flexor planter reflex The subject is asked to relax the muscles of the

legs. A light scratch is given with a thumbnail, a key

or the blunt point of the patellar hammer, along the outer edge of the sole of the foot, from the heel toward the little toe, and then medially along the base of the toes up to the 2nd toe.

Response: planter flexion and drawing together of the toes, often including the big toe, dorsiflexion and inversion of the ankle, and sometimes contraction of the tensor fascia lata. With stronger stimuli the limb may be withdrawn.

Afferent (tebial n.): L5,S1-2. Center: S1-2. Efferent (tebial n.): L4-5 segments.

Extensor planter reflex In infants: the response is a

dorsiflexion of the big toe and retraction of the foot and occasionally dorsiflexion and fan-like spreading of the other toes.

In adults, such a response is seen in lesions of the corticospinal system. This abnormal response is called Babinski sign or positive Babinski.

In this response the dorsiflexion of

the toes is followed by dorsiflexion of the ankle and flexion of the knee and hip.

Note: the stimulus must be applied over the lateral region of the sole because the medial region may give normal response.

Babinski sign may be seen in the following:

Infants below the age of 1 year, i.e., until the corticospinal tracts get myelinated and become functional. The planter response becomes flexor in the next 6-8 months when the child learns to walk.

Upper motor neuron (UMN; corticospinal or pyramidal) lesions: such as cerebral vascular disease.

Spinal cord tumors: the pyramidal fibers are very sensitive to pressure, hence their early involvement in such cases.

Coma due to any cause. Biochemical disturbances: such as hypoglycemia, in which

convulsions may occur.

Abdominal reflexes The subject should be relaxed and in supine position with the abdomen

uncovered. A light scratch with a key or blunt point, is given across the abdominal skin,

directed toward the umbilicus, in the upper, middle and lower regions. Response: a brisk ripple of contraction of the underlying muscles. Centers:

Upper abdominal : T8,9,10 Middle : T9,10,11 Lower abdominal : T10,11,12 segment of the spinal cord.

These reflexes are absent in : UMN lesions above their segmental level in the spinal cord. They may indicate the segmental level of thoracic spinal cord lesion by their absent.

They are difficult to elicit in obese, elderly, anxious subjects and after repeated pregnancies due to loss of muscle tone.

Cremasteric reflexes

a superficial reflex observed in human males.This reflex is elicited by lightly stroking the superior and medial (inner) part of the thigh. The normal response is a contraction of the cremaster muscle that pulls up the scrotum and testis on the side stroked.

5. Deep tendon reflexes

Stimulus: sudden stretch of the muscle spindles, which sends a synchronous volley of impulses from the primary sensory endings into the spinal cord.

In the cord these impulses directly (monosynaptically) stimulate the anterior horn cells which innervate the stretched muscles.

Important: It may be noted that it’s the spindle receptors not the

tendon receptors which are stimulated though the hammer is struck on the tendon and not the muscle belly. All muscles are somewhat excitable to direct mechanical stimulation, which is a direct response and not a stretch reflex. (The tendon receptors respond to excessive stretch- as an inverse stretch reflex, when the muscles relaxes suddenly)

Important stretch reflexes and their spinal Important stretch reflexes and their spinal segmentssegments

Stretch reflex Spinal segment

Biceps reflex C5,6

Brachioradialis reflex C5,6

Triceps reflex C6,7

Patellar reflex (Knee jerk) L3,4

Achilles tendon reflex (Ankle jerk) S1,2

1. The Knee Jerk reflex Supine position:

Legs are semiflexed, and the observer supports both knees by placing a hand behind them. The patellar tendon is then struck midway between the patella and the insertion of the tendon on the tebial tuberosity.

Sitting position: The subject is seated in a chair

and is asked to cross one leg over the other or sit with both legs dangling loosley over the edge of the chair.

Cont…

Response : extension of the knee due to contraction of quadriceps femoris muscle.

Afferent and Efferent paths: femoral nerve.

Centre: L3-4.

2. The Ankle Jerk Sitting position: The examiner slightly dorsiflexes

the foot so as to stretch the Achilles tendon (tendo-calcaneous) and with the other hand, the tendon is struck on its posterior surface.

Supine position: Knee is semiflexed and hip is

externally rotated, the ankle jerks are then tested as described above.

Cont…

Response: planter flexion of the foot due to contraction of the calf muscles.

Afferent and Efferent paths: Tibial nerve.

Centre: S1-2 segments.

3. The Biceps Jerks The subject’s elbow is

flexed to a right angle and the forearm semipronated and supported on the examiners arm.

The examiner then plases his thumb on the biceps tendon and strikes it with the hammer .

Cont…

Response: contraction of the biceps causing flexion and slightly pronation of the forearm.( If the patient is in bed, his forearm may rest across his chest).

Afferent and Efferent paths: musculocutaneous nerve.

Centre: C5-6 cervical segments.

4. The Triceps reflex The arm is flexed to a right

angle and is supported on the examiner’s arm or can be placed on their hips.

The triceps tendon is then struck just proximal to the point of the elbow.

Cont… Response: extension at the elbow. Afferent and Efferent paths: radial nerve. Centre: C6-7

0 No evidence of contraction

1+ Decreased, but still present (hypo-reflexic)

2+ Normal

3+ Super-normal (hyper-reflexic)

4+ Clonus: Repetitive shortening of the muscle after a single stimulation

Reinforcement of the reflexes

The briskness of the deep reflexes varies greatly from one person to person but it’s hardly ever absent in health.

Occasionally it may be very weak or even appear to be absent.

In such cases reinforcement (Jendrassik maneuver)is employed.

Cont…

This is done by asking the subject to perform some strong muscular effort such as clenching the teeth, or locking the fingers of both hands as hard as possible and then trying to pull them apart while the examiner strikes the tendon.

The reflex generally becomes evident.

Cont… Reinforcement acts by increasing the excitability of

the anterior horn cells due to “spilling” over of impulses from the neurons involved in reinforcement effort to the motor neurons of the reflex.

In addition, gamma motor neuron activity increases the sensitivity of the spindle receptors to stretch. It also, perhaps, acting by distracting the subject’s attention.

Tendon reflexes are diminished (hyporeflexia)

in:

Lesions involving afferent pathways.Anterior horn cells (e.g., poliomyelitis).Or efferent pathways.

Tendon reflexes are absent (areflexia)in :

Spinal shock, e.g., sever injury to the cord.

Coma.

Note: deep reflexes may be sluggish or appear to be abolished in some healthy individuals; reinforcement is employed in these cases.

Deep reflexes are exaggerated (hyperreflexia) in:

UMN lesions above the anterior horn cells, especially when the hyperreflexia is unilateral, or accompanied by other signs of UMN disease.

Anxiety or nervousness. Hyperexcitability of the nervous system

(hyperthyroidism ) and tetanus.

Cerebellum Examination

1. Finger to nose test

With eyes open, have patient partially extend elbow and rapidly tip of index finger in a wide arc to tip of his nose.

In cerebellar disease, the action may have an intension tremor.

2. Finger to Finger test

3. Heel to shin test

Patient places one Heel on opposite knee and slides heel down the tibia with foot dorsiflexion.

Movement should be performed accurately.

In cerebellar disease, the arc of the movement is jerky/wavering.

4. Gait

In cerebellar disease, the walk is staggering/wavering or zigzag.

5. Arm-pulling test (rebound test)