Investigations and Management of Rare Treatable Neurological Disorders

1. AR-GCH1 Deficiency Without Hyperphenylalaninaemia

• Presentation: Resembles cerebral palsy, oculogyric crises, tremulousness, bradykinesia.
• Key Investigations:
  • Phenylalanine loading test: Elevated blood spot phenylalanine and phenylalanine/tyrosine ratio.
  • CSF pterins low; monoamine neurotransmitters may be normal.
  • Definitive: Peripheral blood mononuclear or fibroblast GTP cyclohydrolase enzyme assay or mutation analysis.

  2. ACTH Unresponsiveness

  • Presentation: Recurrent encephalopathy, hypoglycemia, epilepsy, subtle joint hyperpigmentation.
  • Key Investigations: ↓ Glucose, ↓ Cortisol, ↑ ACTH.
  • Treatment: Cortisol replacement therapy.

  3. Biotinidase Deficiency

  • Presentation: Epilepsy, developmental delay, neurological deficits, mimics Leigh syndrome ± alopecia, rash.
  • Key Investigations:
    • Brain/spinal cord MRI, urine organic acids.
    • Blood lactate, biotinidase activity assay.

    4. Biotin-Responsive Basal Ganglia Disease

    • Presentation: Rapid motor skill loss, quadriparesis, seizures, akinetic mutism.
    • Key Investigations:
      • Brain MRI: Caudate and putamen necrosis.
      • Mutation in SLC19A3 gene.

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      Published:06 June 2024 Last Updated:08 December 2024