Cerebellar Disorders

Overview

Definition

Cerebellar disorders are a specific set of neurologic signs and symptoms caused by local or systemic conditions that affect the cerebellum; the classic sign is ataxia, in addition to several other motor abnormalities that affect coordination.

Epidemiology

• Inherited/congenital etiologies: usually diagnosed at birth or during infancy
• Vascular etiologies: seen around ≥ 50 years of age
• Both sexes are affected equally, but men display more gait abnormalities. 

Etiologies

• Vascular: posterior circulation stroke (e.g., lateral medullary syndrome)
• Autoimmune: 
  • Multiple sclerosis (demyelination)
  • Systemic lupus erythematosus
  • Sjögren syndrome
• Space-occupying lesions:
  • Posterior fossa tumors (e.g., medulloblastoma, astrocytoma, hemangioblastoma, metastatic lesions)
  • Neurofibromatosis
  • Schwannomas
• Toxic/metabolic:
  • Hypothyroidism 
  • Vitamin B₁₂ deficiency
  • Celiac disease
  • Wilson disease
  • Chronic alcohol use
• Infectious:
  • Enteroviruses
  • HIV (leukoencephalopathy)
  • Neurosyphilis
  • Toxoplasmosis
  • Borreliosis (Lyme disease)
  • Prion diseases (e.g., Creutzfeldt-Jakob disease)
• Inherited/congenital:
  • Ataxia-telangiectasia
  • Friedreich ataxia
  • Von Hippel-Lindau syndrome
  • Chiari malformation
  • Dandy-Walker syndrome
  • Spinocerebellar ataxias
  • Episodic ataxias
• Medications/ingestions:
  • Phenytoin
  • Carbamazepine
  • Lithium
  • Cytarabine (ara-C) chemotherapy
  • Nitrous oxide
  • Alcohol
• Other causes:
  • Gluten enteropathy
  • Paraneoplastic syndromes (e.g., small cell lung cancer)

Pathophysiology and Clinical Presentation

Details regarding pathophysiology and presentation depend on the specific underlying etiology.

Pathophysiology

• Cerebellar injury → loss of adequate cerebellar function ensues → neurologic signs and symptoms related to area of injury
• Symptoms are related to the affected anatomy:
  • Vermis: controls axial equilibrium (balance) → abnormal truncal posture 
  • Hemispheres: control peripheral equilibrium (extremities) → ataxia 
  • Flocculonodular lobe: control eye movements

Clinical presentation

Mnemonic: “DANISH”

• Dysdiadochokinesia (difficulty with rapid alternating movements)/dysmetria (past-pointing)
• Ataxia (unsteady or wide-based gait)
• Nystagmus
• Intention tremor
• Speech (slurred or scanning)
• Hypotonia

Diagnosis

Diagnosis starts with clinical examination findings and is confirmed by diagnostic imaging and/or laboratory studies when warranted by clinical suspicion. 

History

• Symptoms and duration
• Pertinent past medical history
• Medications
• Nutrition
• Substance use: if alcohol-related cerebellar degeneration is suspected, the CAGE (Cut down, Annoyed, Guilty, Eye opener) questionnaire or similar screening may be helpful.

Physical examination

• Complete neurologic exam, including:
  • Eyes:
    • Extraocular movements
    • Evaluate for nystagmus
    • Optic atrophy on fundoscopy (Friedreich ataxia)
  • Cranial nerve testing
  • Evaluate gait:
    • Ataxia/wide-based gait
    • Slow initiation of movement
    • Ataxic “intention” tremor: side-to-side oscillation as movement approaches a target in space
    • Uneven and inconsistent strides, lurching (especially when turning)
  • Listen for dysarthria: 
    • Slurred speech
    • Scanning dysarthria (cerebellar “staccato” speech, with words broken into syllables)
  • Evaluate equilibrium:
    • Romberg sign: difficulty standing with feet together and eyes closed
    • Rapid alternating movements for dysdiadochokinesia
    • Point-to-point movements for dysmetria
  • Muscle tone/motor exam:
    • Hypotonia
    • Loss of muscular power 
    • Postural abnormalities
  • Signs of upper motor neuron disease (demyelination)
  • Sensory exam: peripheral neuropathy may be found.
  • Reflexes
• General physical exam:
  • Signs of hypothyroidism
  • Telangiectasias in the eyes and skin (ataxia-telangiectasia)
  • Mental status exam
  • Hepatomegaly

Testing

• Labs:
  • CBC 
  • Erythrocyte sedimentation rate (ESR)
  • Liver function tests (AST, ALT, alkaline phosphatase (ALP))
  • Vitamin B₁₂ levels
  • Thyroid function (thyroid-stimulating hormone (TSH))
  • Copper levels if Wilson disease is suspected
  • Anti–tissue transglutaminase antibody if celiac disease is suspected
• Consider other tests:
  • Lumbar puncture (CSF assessment)
  • Electromyography (EMG) and nerve conduction studies
  • Visual evoked potentials
  • Genetic testing if:
    • Family history of similar illness 
    • Possible inherited conditions such as Wilson disease
• Imaging: MRI of brain and spinal cord to visualize any demyelinating, vascular, or structural abnormalities

Management and Prognosis

Management

Management of cerebellar disorders requires a multidisciplinary approach, with specialties including neurology, endocrinology, genetics, and/or psychiatry depending on the specific diagnosis. Therefore, management is done by multidisciplinary approach.

• Physical and occupational therapists:
  • Gait training
  • Walking aids
  • Fall prevention measures
  • Coordination and resistance training to improve gait and balance
• Speech therapy for dysarthria 
• Social work or case management 

Complications

• Falls (especially worrisome in the elderly)
• Dizziness
• Paralysis (increased risk of being bedbound)
• Gait disorders
• Worsening tremor

Prognosis

• Depends on the underlying cause
• Metabolic, infectious, toxic, and iatrogenic causes → resolve with appropriate treatment
• Genetic/inherited, vascular, and traumatic causes → long-term effects

Differential Diagnosis

• Parkinson disease: chronic and progressive neurodegenerative disorder that presents clinically with resting tremor, bradykinesia, rigidity, and postural instability. Parkinson disease is diagnosed clinically on the basis of characteristic signs and symptoms. The finding of Lewy bodies in the brain postmortem is the only confirmation for the disease. Treatment includes supportive physical and emotional care plus medications such as levodopa/carbidopa, monoamine oxidase type B inhibitors, and dopamine agonists.
• Major neurocognitive disorder (NCD): also known as dementia. Major neurocognitive disorders are a group of diseases characterized by a decline in a person’s memory and executive function. These disorders are progressive and persistent diseases with several distinct etiologies. The diagnosis is made clinically with mental status testing and often requires interviewing caregivers. Although there are known risk factors and measures to prevent major NCDs, there are no effective curative treatments.
• Amyotrophic lateral sclerosis (ALS): also known as “Lou Gehrig disease.” Amyotrophic lateral sclerosis is a neurodegenerative disease that affects both upper and lower motor neurons and is characterized by signs of lower motor neuron degeneration. The diagnosis is made clinically after other disorders are ruled out. Management is supportive and symptomatic, eventually progressing to end-of-life care. 
• Ischemic stroke: acute neurologic injury resulting from brain ischemia. Ischemic stroke presents with neurologic symptoms with varying degrees of motor and sensory loss corresponding to the area of the brain affected and the extent of tissue damage. Diagnosis is made by physical examination and imaging. Management is ideally with thrombolytic therapy to restore blood flow if the time frame and clinical situation permit. Long-term rehabilitation with physical, occupational, and speech therapy are important after the acute event.