QS Study

The cerebrum is the part of the brain involved in the higher levels of thinking and action. It is involved in the control of voluntary and involuntary movement as well as balance. The cerebellum is located behind the top part of the brain stem and is made of two hemispheres.

Functions of cerebellum

The cerebellum is the area found at the back and bottom of the brain and behind the brainstem. Functionally cerebellum has three parts each of which has a specific function such as –

 (A) Archicerebellum / Vestibulocerebellum.

  • In association with brain stern and spinal cord, it controls equilibrium and postural movements.
  • Concerned with learning-induced changes in the VOR (Vestibulo ocular reflex).

(B) Spinocerebellum

  • In association with the motor cortex, it smoothes and coordinates movements that are ongoing.
  • Control fine movements of hand and fingers.
  • Prevent overshoot of movement and cause ‘damp’ movements, thus prevent intention tremor.

(C) Neocerebellum / Cerebrocerebellum.

  • Interact with motor cortex in planning and programming movements.
  • Provide appropriate timing for each succeeding movement.

Fig: Cerebellum

Signs of a cerebellar lesion

If the nucleus remains intact no sign of leision but leision involving deep nuclei shows two types of sign.

A defect in posture:

  • Hypotonia: Decrease of muscle tone;
  • Past pointing: Overshooting of moving beyond an intended point.
  • Vertigos: Sensation like the surrounding environment is rotating.
  • Nystagmus: Abnormal involuntary jerky movement of the eyeball.
  • Defective attitude: Face move towards the opposite side.

The defect in Voluntary Movement:

  • Asthenia: Weakness of movement,
  • Ataxia: In coordination of movement,
  • Reeling gait: Leg wide apart and deviates to the same side.
  • Intention tremor: Oscillation of organ during voluntary movement.
  • Dysarthria: Scanning speech.
  • Dysdiadochokinesia: Inability to rapid pronation and supination of hand.

Test for cerebellar lesions:

  • Finger-nose test,
  • Dysdiadochokinesia
  • Gait test
  • Speech test
  • Heel-shin test.