In a 13-year-old girl with bright foci on brain MRI, chronic fatigue, intermittent nausea and vomiting, and mild ocular deviation on waking, what is the most likely diagnosis and what urgent neuro‑imaging and specialist evaluation are recommended?

Urgent Evaluation for Suspected Increased Intracranial Pressure or Posterior Fossa Pathology

This 13-year-old girl requires immediate comprehensive brain MRI with and without contrast, urgent pediatric neurology consultation, and ophthalmologic examination to rule out a posterior fossa tumor, diffuse high-grade glioma, or idiopathic intracranial hypertension—all of which can present with this constellation of symptoms and carry significant morbidity if diagnosis is delayed.

Most Likely Differential Diagnoses

The combination of bright spots on MRI, chronic fatigue, nausea/vomiting, and cranial nerve involvement (ocular deviation) in a 13-year-old strongly suggests:

Tier 1: Life-Threatening Conditions Requiring Urgent Action

• Posterior fossa tumor (most concerning): Occipital headache with vomiting, progressive fatigue over weeks to months, and cranial nerve deficits are classic presentations 1. The "bright spots" may represent tumor, edema, or associated hydrocephalus 2.

• Pediatric diffuse high-grade glioma: Presents with symptoms of increased intracranial pressure (nausea, vomiting), fatigue, personality changes, and cranial nerve deficits 2. School-age children specifically experience fatigue and poor school performance as presenting features 2.

• Acute hydrocephalus: Nausea, vomiting, and fatigue from increased intracranial pressure; represents a neurosurgical emergency 1.

Tier 2: Serious Conditions to Exclude

• Idiopathic intracranial hypertension (IIH): Most commonly affects females of childbearing age, presents with visual disturbances and papilledema 3. The ocular deviation on waking could represent abducens nerve palsy from raised pressure 3.

• Neuromyelitis optica (NMO): Can present with atypical symptoms including behavioral changes and vomiting in adolescent girls 4. In pediatric NMO, 55% have clinical demyelinating episodes involving the brain, and 75% show abnormal brain MRI by follow-up 5. The "bright spots" could represent demyelinating lesions 5.

• Multiple sclerosis: T2-hyperintense foci are characteristic, though less common in this age group 6.

Immediate Diagnostic Work-Up

Neuroimaging Protocol

MRI brain with and without intravenous contrast is mandatory and should be performed urgently 1. This is superior to CT for detecting posterior fossa abnormalities, which are missed in up to 71% of cases on initial CT 2.

Specific MRI sequences required:

• T1-weighted pre- and post-contrast
• T2-weighted and FLAIR sequences (sensitive for vasogenic edema and white matter lesions) 1
• Diffusion-weighted imaging (detects cytotoxic edema) 1
• Dedicated orbital imaging to assess optic nerve sheaths for papilledema 3

If initial MRI shows only nonspecific white matter lesions, add:

• MR venography to exclude cerebral venous thrombosis, which can be missed on routine MRI 1
• Spinal MRI if NMO is suspected (look for longitudinally extensive transverse myelitis) 5

Urgent Ophthalmologic Examination

Fundoscopy to assess for papilledema is critical 1, 3. Papilledema signals increased intracranial pressure and mandates imaging before any lumbar puncture to avoid herniation 1.

The ocular deviation on waking may represent:

• Abducens nerve palsy from raised intracranial pressure 3
• Direct cranial nerve involvement by tumor 2
• Internuclear ophthalmoplegia from demyelinating disease 5

Laboratory Evaluation

• Aquaporin-4 antibody (AQP4-Ab) if NMO is suspected: AQP4-Ab positive cases have mean time to relapse of 0.76 years and severe visual impairment 5
• Complete blood count, comprehensive metabolic panel
• ESR/CRP if vasculitis is considered 6

Red Flags Present in This Case

This patient has multiple concerning features that mandate urgent evaluation 2, 1:

1. Age >3 years with chronic symptoms: Higher yield of clinically significant findings 2
2. Cranial nerve involvement (ocular deviation): Focal neurological deficit pointing toward tumor, stroke, or raised intracranial pressure 1
3. Chronic progressive symptoms: Fatigue and nausea worsening over time suggests space-occupying lesion 2
4. Nausea and vomiting: Classic signs of increased intracranial pressure or posterior fossa pathology 2, 1

Management Algorithm Based on Imaging Results

If MRI Shows Mass Lesion or Tumor

1. Immediate neurosurgical consultation 2
2. Goals of surgery: Safe reduction of tumor-associated mass effect and obtaining tissue for histologic and molecular classification 2
3. Referral for cancer predisposition evaluation should be considered 2
4. Treatment depends on pathology: For pediatric diffuse high-grade gliomas in patients ≥3 years, standard treatment is brain RT + concurrent temozolomide + adjuvant temozolomide ± lomustine, though clinical trial enrollment is preferred 2

If MRI Shows Only Nonspecific White Matter Lesions

1. Perform MR venography to exclude cerebral venous thrombosis 1
2. Test AQP4-Ab for NMO: Early testing allows prompt immunomodulatory treatment to minimize disability 5
3. Consider lumbar puncture only after confirming no papilledema and no mass effect: Opening pressure >280 mm CSF in children suggests IIH 3

If MRI Shows Signs of Idiopathic Intracranial Hypertension

Secondary MRI signs include: empty sella, dilated optic sheaths, tortuous or enhancing optic nerves, flattening of posterior globes, transverse sinus stenosis 3

Diagnostic confirmation requires:

• Lumbar puncture with opening pressure >280 mm CSF 3
• Normal CSF composition 3
• Papilledema on fundoscopy 3

Initial treatment:

• Weight loss if overweight 7
• Acetazolamide as first-line medical therapy 7

Critical Pitfalls to Avoid

1. Do NOT dismiss this as migraine or tension headache: While headache on waking alone in neurologically normal children rarely indicates pathology 8, this patient has additional red flags (cranial nerve deficit, chronic fatigue, bright spots on MRI) that mandate full evaluation 2, 1.

2. Do NOT perform lumbar puncture before imaging if focal deficits or altered consciousness are present: Risk of herniation 1.

3. Do NOT assume normal routine MRI excludes cerebral venous thrombosis: Dedicated venography is required 1.

4. Do NOT delay neurosurgical consultation if tumor is identified: Posterior fossa tumors can cause acute hydrocephalus and herniation 2, 1.

5. Incidental white matter lesions are common (18% of asymptomatic volunteers have abnormal MRI findings) 9, but in the context of this patient's symptoms, they require full investigation 6.

Disposition

Admit for urgent evaluation given multiple red flags, abnormal neuroimaging, and need for subspecialty consultation 1. This patient requires:

• Urgent pediatric neurology evaluation
• Ophthalmology assessment for papilledema
• Neurosurgery consultation if mass lesion identified
• Possible lumbar puncture after imaging excludes mass effect

Do NOT discharge until life-threatening causes are excluded and a definitive diagnosis is established 1.