Cerebellar syndromes

The cerebellum is the region of the brain responsible for controlling stance, gait, and balance, as well as the coordination of complex and goal-directed movements. The acute onset of cerebellar symptoms is considered a medical emergency and is usually due to stroke, hemorrhage, or cerebral edema. Chronic cerebellar syndromes are either acquired (e.g., alcoholism, tumors, paraneoplastic) or genetic. Cerebellar injury is characterized by impaired cerebellar function, resulting in ataxia, imbalance, uncoordinated movements (dysmetria), speech (dysarthria), and oculomotor disorders (nystagmus). Vertigo may also occur if the vestibulocerebellar system is affected. The diagnosis is based on the evaluation of these symptoms and is confirmed by detection of the underlying cause in imaging or laboratory or genetic tests. As treatment of these causes is often not possible, management is focused on supportive measures such as physiotherapy and psychological support groups.

• Acute
  • Infarction, TIA
  • Head trauma, edema, hemorrhage
  • Infections (acute postviral cerebellitis), including:
    • Adults: VZV, EBV, Lyme disease, tertiary syphilis; , malaria, prion diseases (e.g., Creutzfeldt-Jakob disease)
    • Children: VZV , coxsackievirus, parvovirus B19, HHV-6, hepatitis A, enteroviruses, measles, mumps, Lyme disease, etc.
  • Medication, toxins, and poisons: barbiturates, benzodiazepines, heavy metals, and chemotherapy
• Subacute and chronic
  • Alcoholism
  • Intracranial tumors (e.g., medulloblastoma)
  • Vitamin deficiencies: vitamin B12 deficiency, vitamin B1 deficiency (Wernicke encephalopathy)
  • Paraneoplastic cerebellar degeneration
  • Genetic: Friedreich ataxia, ataxia telangiectasia, spinocerebellar ataxia,
  • Multiple sclerosis
  • Wilson disease (rare)

The clinical features vary depending on the underlying cause and severity of cerebellar injury. Symptoms manifest ipsilaterally to the site of the lesion.

• Cerebellar ataxia
  • Gait ataxia
    • Abnormal wide-based and unsteady gait; irregular, uncoordinated activity of the muscles of pelvic girdle and/or lower limbs
    • Unsteadiness that occurs independently of whether the eyes are open or closed (Romberg test cannot be performed)
  • Truncal ataxia
    • Inability to maintain truncal stability and coordinate central trunk muscles, which manifests in difficulty sitting upright and/or standing without support; most apparent in the sitting position
    • Occurs due to damage to the cerebellar vermis
  • Limb ataxia
    • The inability to perform coordinated movements with the upper and/or lower extremities
    • Can manifest with dysmetria: the inability to coordinate the speed and range of a certain movement. The patient tends to overshoot (hypermetria) or miss (hypometria) their target.
    • Positive finger-to-nose test: patients are unable to touch the tip of their nose with their index finger with eyes closed
    • Positive heel-knee-shin test: patients are unable to run the heel of one foot down the shin of the other leg, resulting in characteristic zig-zag movements of the foot as a result of excessive corrective movements to counterbalance deviation.
    • Occurs due to damage to the cerebellar hemispheres
• Tremor (postural, action, intention tremor): patients with tremor perform the finger-to-nose test with shaking fingers
• Dysdiadochokinesia
  • Inability to perform rapidly alternating agonistic-antagonistic movements
  • Positive rapid alternating movement test: the patient is unable to rapidly screw in an imaginary large light bulb using both hands (slow, uncoordinated movements)
• Rebound phenomenon (Stewart-Holmes sign)
  • The patient is asked to flex their elbow against resistance applied by the examiner pulling the forearm in the opposite direction; sudden release of the arm by the examiner results in an overshooting movement.
• Pendular knee jerk
  • Abnormally increased patellar reflex
  • Leg movement persists beyond initial reflex triggering
• Cerebellar drift: the patient is asked to extend their supinated arms at shoulder level; the arm ipsilateral to the lesion will pronate and drift upwards. ^[1]
• Dysarthria (scanning speech): words are broken down into separate syllables and spoken with varying force
• Oculomotor dysfunction (including nystagmus)
• Acute cerebellar hemorrhage
  • Occipital headache
  • Neck stiffness
  • Vomiting
  • Nystagmus
  • Gait ataxia
• Other
  • Vertigo
  • Muscular hypotonia

The localization of symptoms offers important diagnostic clues. Unilateral abnormalities in ocular movements, ataxia, and posture indicate a cerebellar lesion on the ipsilateral side.

Cerebellar syndromes are primarily a clinical diagnosis, based especially on the evaluation of posture, gait, and movements. Imaging tests and laboratory studies confirm the diagnosis.

• Neuroimaging (CT/MRI): indicated to rule out infarction, hemorrhage, tumors, edema
• Laboratory testing: complete blood cell count; electrolytes, vitamin B₁₂ levels, vitamin B₁ levels
• Genetic testing: if other diagnostic tests are negative or inconclusive

The differential diagnoses listed here are not exhaustive.