Cerebellar Lesions and Clinical Dysfunction

Anatomical Zones and Presenting Symptoms

The cerebellum can be divided into three distinct functional zones, each associated with specific clinical deficits when damaged.

• Vestibulocerebellum (Flocculonodular Lobe): Responsible for posture, balance, and the control of eye movements. Lesions here typically cause truncal ataxia (instability while sitting or standing) and nystagmus.
• Spinocerebellum (Vermis and Paravermis): Regulates gross limb movements and muscle tone. Damage to the midline vermis often results in a broad-based, unsteady gait without significant ataxia of the upper limbs.
• Cerebrocerebellum (Lateral Hemispheres): Vital for planning and coordinating complex, fine voluntary movements. Lateral lesions present with appendicular ataxia, affecting the precise movement of the arms and legs.

The DANISH Mnemonic

The classic signs of cerebellar hemisphere dysfunction are often remembered using the acronym DANISH, which outlines the hallmark neurological examination findings.

• Dysdiadochokinesia: The inability to perform rapid alternating movements, such as flipping the hands back and forth on the thighs.
• Ataxia: A lack of voluntary coordination of muscle movements, leading to a clumsy or staggering gait.
• Nystagmus: Rhythmic, involuntary oscillatory eye movements, typically gaze-evoked and most prominent when looking toward the side of the lesion.
• Intention Tremor: A broad, coarse tremor that becomes progressively worse as the patient's hand approaches a target, such as during the finger-to-nose test.
• Slurred Speech (Dysarthria): Scanning speech, characterized by inappropriate variations in volume, erratic word spacing, and poor articulation.
• Hypotonia: Decreased muscle tone, leading to pendular reflexes where a limb swings multiple times after a deep tendon reflex is elicited.