Conditions diagnosable clinically without imaging: Migraine, tension-type headaches, medication overuse headaches, post-traumatic headaches.

Rationale: Incidental findings on scans may cause unnecessary anxiety, and normal scans do not resolve headaches.

Why this matters: Avoids unnecessary radiation (CT) and focuses on clinical diagnosis.

• CT scan: Detects large tumors, abscesses, hydrocephalus, hemorrhage (e.g., subarachnoid hemorrhage).

• Limitation: High radiation dose (equivalent to 200 chest X-rays). MRI is preferred electively.
  Why this matters: Rapidly identifies life-threatening causes (e.g., hemorrhage).

• MRI head scan: Identifies structural causes (e.g., tumors, cortical dysplasia).

• EEG role: Less useful in adults but informative in pediatric/adolescent epilepsy.
  Why this matters: Structural lesions (e.g., tumors) are common in late-onset epilepsy.

• Contraindications: Papilloedema, focal neurological signs, impaired consciousness (risk of brain herniation from raised ICP).

• Action: Perform brain imaging (CT/MRI) before lumbar puncture (LP).
  Why this matters: Prevents fatal complications like brainstem herniation.

• Key findings: Elevated neutrophils, low glucose (compared to blood glucose), high protein, positive Gram stain/culture.

• Immediate action: Start antibiotics before imaging if bacterial meningitis is suspected.
  Why this matters: Delayed treatment increases mortality.

• LP for xanthochromia: Perform LP ≥12 hours post-bleed to detect bilirubin/oxyhemoglobin (spectroscopy or visual xanthochromia).

• Avoids confusion: Distinguishes SAH from traumatic LP (fresh RBCs vs. lysed RBCs).
  Why this matters: CT misses 5–10% of SAH cases; LP is diagnostic.

• Primary use: Distinguishes generalized vs. focal epilepsy (e.g., spike-wave patterns).

• Limitations: Interictal EEG may be normal; video telemetry is needed for frequent undiagnosed episodes.
  Why this matters: Guides antiepileptic drug choice (e.g., broad-spectrum vs. focal agents).

Indications:

• Confirm carpal tunnel syndrome (median nerve entrapment).

• Differentiate axonal vs. demyelinating polyneuropathy (e.g., Guillain-Barré vs. CIDP).

• Evaluate suspected neuromuscular junction disorders (e.g., myasthenia gravis).
  Why this matters: Guides surgical (e.g., decompression) or medical (e.g., IVIG) management.

   

• Oligoclonal bands: IgG bands in CSF (not serum) indicate intrathecal synthesis.

• Cell count: Mild lymphocytosis (<50 cells/mm³).
  Why this matters: Supports MS diagnosis when MRI is equivocal or lesions are nonspecific.

• Albuminocytologic dissociation: Elevated protein (>0.55 g/L) without pleocytosis.

• Timing: Protein rises 1–2 weeks after symptom onset; early LP may miss this.
  Why this matters: Differentiates GBS from infectious/inflammatory polyradiculopathies.

• Muscle edema/inflammation: Identifies inflammatory myopathies (e.g., dermatomyositis).

• Biopsy guidance: Targets affected muscles for sampling.
  Why this matters: Avoids sampling errors in patchy diseases (e.g., muscular dystrophy).

   

• Bacterial vs. viral meningitis: Elevated lactate suggests bacterial infection.

• Mitochondrial disorders: Elevated CSF lactate in mitochondrial encephalopathies.
  Why this matters: Complements glucose and cell count in ambiguous cases.

• SAH diagnosis: "Wait 12 hours for xanthochromia."

• GBS CSF: "High protein, no cells."

• MS CSF: "Oligoclonal bands ≠ serum."

• CT vs. MRI: CT for emergencies (hemorrhage), MRI for detail (tumors, MS plaques).

• LP timing: Always image first if raised ICP suspected.

• EEG pitfalls: Normal interictal EEG ≠ no epilepsy

• Structural imaging (MRI/CT): Rule out vascular, neoplastic, or degenerative causes.

• Metabolic imaging (PET): Assess glucose metabolism.

• Molecular imaging (amyloid PET): Emerging tool for Alzheimer’s diagnosis.
  Why this matters: Differentiates Alzheimer’s (amyloid plaques) from vascular dementia.

• Indications: Spinal cord symptoms (e.g., myelitis) or equivocal brain MRI findings.
  Why this matters: Spinal lesions support MS diagnosis and exclude mimics like transverse myelitis.

• Guides biopsy: Identifies inflamed/affected muscles (e.g., inflammatory myopathies).

• Assesses disease extent: Differentiates dystrophies from metabolic myopathies.
  Why this matters: Avoids sampling error in patchy diseases (e.g., polymyositis).

• Non-contrast CT: Rules out hemorrhage for thrombolysis eligibility.

• CT angiography/MRI: Identifies salvageable penumbra and occluded vessels.
  Why this matters: Guides urgent thrombolysis or thrombectomy.

When is video telemetry essential in epilepsy diagnosis?

• Indications: Differentiate epileptic vs. non-epileptic attacks (e.g., psychogenic seizures).

• Requirement: High attack frequency to capture events.
  Why this matters: Prevents misdiagnosis and inappropriate antiepileptic use.

• Periodic sharp wave complexes (PSWCs): 1–2 Hz generalized spikes.

• Supportive CSF marker: 14-3-3 protein.

• Real-time quaking-induced conversion (RT-QuIC) is a highly sensitive assay for prion protein.
  Why this matters: Rapidly progressive dementia with characteristic EEG changes.

   

• Denervation: Fibrillations, positive sharp waves, reduced recruitment.

• Myopathy: Small, short-duration motor units, early recruitment.
  Why this matters: Differentiates ALS (denervation) from muscular dystrophy.

• Anticoagulation/bleeding disorders: Risk of hematoma.

• Infection at needle site: Risk of spreading.
  Why this matters: Prioritizes patient safety during invasive testing.

   

• Send 3 consecutive CSF samples: For acid-fast bacilli (AFB) stain, PCR, and culture.

• Findings: Lymphocytosis, low glucose, high protein.
  Why this matters: Delayed treatment increases mortality; cultures take weeks.

• Elevated tau, reduced amyloid-beta: High tau:amyloid ratio.
  Why this matters: Supports diagnosis when clinical/MRI findings are ambiguous.

• CSF cytology: Malignant cells (send 3 serial samples).

• Findings: High protein, low glucose.
  Why this matters: Metastatic cancer/lymphoma requires urgent intrathecal chemotherapy.

• CIDP: Persistently high CSF protein without pleocytosis.

• GBS: Albuminocytologic dissociation (high protein, normal cells).
  Why this matters: CIDP requires long-term immunotherapy (e.g., IVIG).

• Pressure: 5–20 cm H₂O.

• Cells: <5 lymphocytes/mm³.

• Glucose: 60–70% of serum glucose.

• Protein: 0.15–0.45 g/L.
  Why this matters: Baseline for diagnosing infections/inflammation.

• Bed rest, hydration, caffeine.

• Blood patch: For refractory cases.
  Why this matters: Common complication (10–30% of LPs); self-limiting but debilitating.

• Brachial/lumbosacral plexopathy: Trauma, neoplasms (e.g., Pancoast tumor).

• MRI: Gold standard; CT for bony involvement.
  Why this matters: Identifies surgically treatable lesions (e.g., nerve sheath tumors).