Investigation for NBAI (Non-Bilious Abdominal Illness / Hypertrophic Pyloric Stenosis)

History & Clinical Clues

• Projectile, non-bilious vomiting in a neonate (typically 2–8 weeks old)
• First-born male infant (4:1 male predominance)
• Hungry after vomiting
• Visible peristaltic wave (left to right) after feeding
• Palpable "olive-shaped" mass in the epigastrium

Investigations

1. Blood Tests (Metabolic Workup)

Classic metabolic derangement: Hypochloremic, hypokalemic metabolic alkalosis with paradoxical aciduria

2. Ultrasound Abdomen (Investigation of Choice)

• Pyloric muscle thickness ≥ 4 mm (abnormal)
• Pyloric channel length ≥ 16 mm (abnormal)
• Pyloric diameter ≥ 13 mm
• "Target sign" or "doughnut sign" on transverse view
• Failure of pyloric canal to open during real-time observation

Ultrasound has sensitivity ~97%, specificity ~100% for pyloric stenosis.

3. Upper GI Contrast Study (Barium Meal) — if ultrasound inconclusive

• "String sign" — thin elongated pyloric channel
• "Shoulder sign" — pyloric mass indenting gastric antrum
• "Double track sign" — two parallel streaks of contrast
• Delayed gastric emptying

4. Plain Abdominal X-ray

• Distended stomach with little distal gas
• Not diagnostic but helpful to exclude other causes (e.g., duodenal atresia — "double bubble")

5. Urine

• Paradoxical aciduria — urine is acidic despite systemic alkalosis (due to hydrogen ion secretion in exchange for sodium, to preserve volume)

Differential Diagnoses to Exclude

• Gastroesophageal reflux (most common mimic)
• Overfeeding
• Adrenal insufficiency (congenital adrenal hyperplasia — check 17-OHP)
• Duodenal web
• Antral web

Management (after stabilization)

• Correct electrolyte imbalance first (surgery is never an emergency until metabolic status normalized)
• Definitive treatment: Ramstedt's pyloromyotomy (open or laparoscopic)

Note: If NBAI refers to a different condition in your curriculum (e.g., a specific institutional abbreviation), please clarify and I'll tailor the answer accordingly.

Neurodegeneration with Brain Iron Accumulation (NBIA)

Subtypes & Genetics

Clinical Features

• Dystonia (most prominent feature)
• Parkinsonism — rigidity, bradykinesia
• Spasticity
• Neuropsychiatric abnormalities — behavioral changes, cognitive decline
• Retinal degeneration (especially in PKAN)
• Cerebellar dysfunction
• Presentation usually in childhood, though adult-onset cases exist
• Course is progressive

Investigations

1. MRI Brain (Key Investigation)

• T2-weighted MRI shows:
  • Hypointensity in the globus pallidus and substantia nigra (due to iron deposition)
  • "Eye-of-the-Tiger" sign — pathognomonic for PKAN:
    • Central hyperintense area (gliosis/neuronal loss) surrounded by hypointense ring (iron) in the globus pallidus

Axial T2 MRI showing the pathognomonic "eye-of-the-tiger" sign: bilateral globus pallidus hypointensity with central hyperintense focus, classic for PKAN/NBIA.

• Gradient echo (GRE) / SWI sequences — more sensitive for iron detection

2. Genetic Testing

• Confirmatory — gene panel or whole exome sequencing
• PANK2 mutation testing for PKAN (most common)
• Next-generation sequencing (NGS) panel for all known NBIA genes

3. Ophthalmological Examination

• Retinitis pigmentosa in PKAN
• Optic atrophy

4. Neurophysiology

• EEG — may show non-specific abnormalities
• Nerve conduction studies/EMG — axonal neuropathy in some subtypes (e.g., PLAN)

5. Blood & Biochemical Tests

• Serum ceruloplasmin and copper (to exclude Wilson's disease and aceruloplasminemia)
• Serum ferritin — elevated in neuroferritinopathy
• Acanthocytes on peripheral blood smear (in PKAN/MPAN — "HARP syndrome" variant)
• Serum iron studies

6. CSF Analysis

• Not specific, but may show elevated ferritin in some cases

7. Skin/Conjunctival Biopsy

• Rarely used; may show iron deposits or specific ultrastructural changes

Key Differentials

• Wilson's disease
• Huntington's disease
• Primary dystonia (DYT1)
• Juvenile Parkinson's disease
• Multiple system atrophy

Management (Symptomatic — No Cure)

• Dystonia: Trihexyphenidyl, baclofen, botulinum toxin, deep brain stimulation (DBS)
• Parkinsonism: Levodopa (limited response)
• Iron chelation (e.g., deferiprone) — under investigation; some benefit seen in PKAN
• Physiotherapy, speech therapy, occupational therapy
• Genetic counseling for family members

The "eye-of-the-tiger" sign on T2 MRI is the single most important investigation finding in NBIA, particularly PKAN, and is essentially diagnostic when present in the right clinical context.