What are the causes and management of Cerebellar Hemispheric Syndrome?

Causes of Cerebellar Hemispheric Syndrome

Cerebellar hemispheric syndrome is primarily caused by vascular events (stroke), tumors, inflammatory/infectious processes, and medication-induced neurotoxicity, with stroke being the most common etiology requiring prompt diagnosis and management to reduce mortality and morbidity.

Vascular Causes

Vascular pathologies represent the most common cause of cerebellar hemispheric syndrome:

• Cerebellar infarction: Occlusion of cerebellar arteries (posterior inferior cerebellar, anterior inferior cerebellar, or superior cerebellar arteries) 1
• Hemorrhagic transformation: Common complication of severe stroke involving matrix metalloproteinases and inflammatory mediators 1
• Multiple infarcts: Can cause bilateral cerebellar involvement 1

Inflammatory/Infectious Causes

• Viral infections: Including herpes simplex virus, varicella zoster virus, HIV 1
• Bacterial infections: Including Lyme disease, tuberculosis, syphilis 1
• Hemicerebellitis: Acute inflammation of a single cerebellar hemisphere, particularly in pediatric populations 2
• Autoimmune disorders:
  • Autoimmune inner ear disease with cerebellar involvement 1
  • Multiple sclerosis (though isolated eighth nerve palsy is extremely rare <1%) 1, 3
  • Cogan's syndrome (non-syphilitic interstitial keratitis with hearing loss and vertigo) 1

Medication/Treatment-Induced Causes

• Chemotherapeutic agents:
  • High-dose cytarabine (most common) 1
  • Bortezomib, rituximab, and trastuzumab (rare) 1
• Risk factors for medication-induced cerebellar syndrome:
  • Liver and renal impairment
  • Very high antineoplastic drug doses
  • Age >40 years 1

Neoplastic Causes

• Primary tumors: Cerebellar astrocytomas, medulloblastomas, hemangioblastomas
• Metastatic disease: From lung, breast, and other primary cancers
• Paraneoplastic syndromes: Associated with occult malignancies
• Bilateral vestibular schwannomas: Associated with neurofibromatosis type II 1
• Carcinomatous meningitis 1

Congenital/Developmental Causes

• Cerebellar hemispheric dysplasia: Rare developmental abnormality with disorganized architecture and foliation 4
• Genetic disorders: Both syndromic and non-syndromic forms that may present later in life 1
• Mitochondrial disorders: Including MELAS (metabolic encephalopathy, lactic acidosis, and stroke-like episodes) 1

Other Causes

• Toxic exposure: Lead poisoning can cause cerebellar dysfunction 1
• Degenerative diseases: Including spinocerebellar ataxias 5
• Trauma: Cerebellar contusion or hemorrhage following head injury 1

Clinical Presentation

Cerebellar hemispheric syndrome typically presents with:

• Ipsilateral limb ataxia
• Dysmetria and intention tremor
• Dysarthria
• Nystagmus
• Vertigo with nausea and vomiting 1, 6

Diagnostic Approach

1. MRI brain: Preferred initial imaging modality for evaluation of cerebellar ataxia 6
   • Note: Initial CT can be normal in up to 25% of patients with cerebellar infarction 6
2. CSF analysis: To exclude CNS infection when suspected 1
3. Laboratory tests: To identify underlying causes (infectious, autoimmune, toxic)

Management Considerations

Management depends on the underlying cause:

• For cerebellar stroke with swelling:

  • Monitor for neurological deterioration (usually within 72-96 hours) 1
  • Maintain normothermia and normoglycemia 1
  • Consider surgical decompression for significant mass effect 1

• For medication-induced cerebellar syndrome:

  • Discontinue the causative agent immediately 1
  • Recovery is variable, ranging from complete remission to persistent disabling ataxia 1

• For inflammatory causes:

  • Treat underlying infection if identified
  • Consider corticosteroids for autoimmune processes

Important Caveats

• Deterioration in level of consciousness is the most reliable clinical indicator of tissue swelling and requires urgent attention 6
• Cerebellar stroke can mimic more benign conditions like gastroenteritis due to prominent nausea and vomiting 6
• Truncal ataxia is often missed during bedside examination if not specifically tested 6
• Cerebellar lesions can sometimes present with signs that mimic cerebral hemisphere dysfunction 7

Early recognition and appropriate management of cerebellar hemispheric syndrome are crucial to prevent potentially life-threatening complications such as brainstem compression and hydrocephalus.