What is Fahr disease?

Fahr's Disease

Fahr's disease is a rare neurological disorder characterized by abnormal calcified deposits in the basal ganglia, dentate nuclei of the cerebellum, and cerebral cortex, leading to progressive neurological dysfunction. 1

Clinical Characteristics

Pathophysiology

• Abnormal calcium deposits (calcium carbonate and calcium phosphate) primarily affect:
  • Basal ganglia
  • Thalamus
  • Hippocampus
  • Cerebral cortex
  • Cerebellar subcortical white matter
  • Dentate nucleus 1

Demographics

• Typically affects young to middle-aged adults 1
• Can present late in life, with cases reported in elderly patients 2

Clinical Manifestations

Fahr's disease presents with a wide spectrum of symptoms:

1. Neurological symptoms:

   • Movement disorders including Parkinsonism, chorea, and tremors
   • Dystonia
   • Ataxia
   • Seizures
   • Impaired eye movements 1, 2

2. Neuropsychiatric manifestations:

   • Memory and concentration deficits
   • Dementia
   • Behavioral abnormalities
   • Psychosis and hallucinations
   • Confusion and altered mental status 3, 4, 2

3. Other presentations:

   • Speech abnormalities
   • Gait disturbances 4

Diagnostic Criteria

The diagnosis of Fahr's disease is based on the following criteria:

1. Bilateral calcification of basal ganglia
2. Progressive neurologic dysfunction
3. Absence of biochemical abnormalities
4. Absence of infectious, traumatic, or toxic causes
5. Significant family history 1

Diagnostic Imaging

• CT scan: Most sensitive for detecting calcifications; shows extensive bilateral calcifications in the basal ganglia, dentate nuclei, and subcortical white matter
• MRI: Complementary to CT but less sensitive for calcifications
• Plain radiography: May show calcifications but less sensitive than CT 1, 4

Laboratory Investigations

• Complete blood count
• Serum calcium, phosphorus, alkaline phosphatase
• Parathyroid hormone levels (to rule out hypoparathyroidism)
• Thyroid function tests
• Cerebrospinal fluid analysis (if indicated) 1, 5

Differential Diagnosis

Important to distinguish from secondary causes of brain calcification:

• Hypoparathyroidism and pseudohypoparathyroidism
• Endocrine disorders
• Mitochondrial myopathies
• Infectious diseases
• Toxic exposures 1, 5

Management

Currently, there is no specific cure for Fahr's disease. Management focuses on:

1. Symptomatic treatment:

   • Movement disorders: Appropriate medications based on specific symptoms
   • Psychiatric symptoms: Antipsychotics, antidepressants as needed
   • Seizures: Anticonvulsants if present 1

2. Treatment of underlying causes:

   • If secondary to hypoparathyroidism: Calcium and vitamin D supplementation 5

3. Supportive care:

   • Physical therapy for movement disorders
   • Cognitive rehabilitation for cognitive impairment
   • Psychological support 1

Prognosis

• The disease is progressive with variable rates of deterioration
• Some evidence suggests early diagnosis and treatment of underlying causes (if present) may reverse calcification and improve mental function 1

Genetic Counseling

• Families with known history of Fahr's disease should receive genetic counseling
• The disease may have autosomal dominant or recessive inheritance patterns
• Molecular genetics of this disease have not been extensively studied 1, 4

Key Clinical Considerations

• Consider Fahr's disease in patients presenting with unexplained movement disorders and/or neuropsychiatric symptoms
• Brain imaging is essential for diagnosis when clinical suspicion exists
• Always rule out secondary causes of brain calcification, particularly endocrine disorders like hypoparathyroidism
• Early diagnosis may lead to better management of symptoms and potentially slow disease progression 1, 3, 5