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Information

 Differential Diagnosis of Nervous System Disorders

Extraaxial Tumor  !!navigator!!

mnemonic: MABEL

  • Meningioma
  • Arachnoid cyst
  • Bony lesion
  • Epidermoid
  • Leukemic / lymphomatous infiltration

Low-attenuation Extraaxial Lesion

  1. Acoustic schwannoma (occasionally low-density mass)
  2. Epidermoid tumor
  3. Arachnoid cyst

Pericerebral Fluid Collection in Childhood  !!navigator!!

  1. ENLARGED SUBARACHNOID SPACE
    1. due to macrocephaly
      1. Benign macrocephaly of infancy
    2. due to brain atrophy
    • superficial cortical veins cross subarachnoid space to reach superior sagittal sinus
    • wide sulci, normal configuration of gyri
    • normal / prominent size of ventricles
  2. SUBDURAL FLUID COLLECTION
    1. Subdural hygroma
    2. Subdural empyema / abscess ← meningitis
    3. Subdural hematoma
    • superficial cortical veins are prevented from crossing the subarachnoid space by the presence of arachnoid / neomembrane
    • wide interhemispheric fissure

Subdural Fluid Collection

  1. Hyperdense = acute subdural hematoma
  2. Isodense = subacute subdural hematoma
  3. Hypodense
    1. Chronic subdural hematoma
    2. Subdural hygroma
    3. Effusion from meningoencephalitis

Jugular Foramen Mass  !!navigator!!

  1. NONNEOPLASTIC ENTITIES
    1. Asymmetrically enlarged jugular foramen
    2. High-riding jugular bulb
      • dome of bulb reaches above internal acoustic canal
      • thin osseous plate separates jugular bulb from middle ear cavity (thin-section CT!)
    3. Dehiscent jugular bulb
      • pulsatile tinnitus
      • vascular tympanic membrane
      • middle ear soft-tissue mass contiguous with jugular foramen (= jugular bulb bulges into middle ear cavity)

        Intra- versus Extraaxial Mass

        IntraaxialExtraaxial
        Relationship to durano attachment until advancedcontiguous
        Local bony changesuncommoncommon
        Cortex displacedtoward boneaway from bone, buckling of gray + white matter, displacement of vessels
        Subarachnoid cisterneffacedwidened, CSF cleft
        Feeding arteriespialdural
      • absence of bony plate separating jugular bulb from posteroinferior middle ear cavity

      DDx: Jugular megabulb (rises above floor of EAC but with preservation of bony plate)
    4. Jugular vein thrombosis
  2. NEOPLASM
    1. Paraganglioma = glomus tumor
    2. Nerve sheath tumor = neuroma
    3. Meningioma
    4. Vascular metastasis (renal / thyroid cancer)
  3. PRIMARY BONE LESION
    1. Multiple myeloma
    2. Lymphoma
    3. Langerhans cell histiocytosis

Cerebellopontine Angle Tumor  !!navigator!!

= extraaxial tumor arising in CSF-filled space bound by pons + cerebellar hemisphere + petrous bone

Frequency: 5–10% of all intracranial tumors

  • cranial neuropathy: high frequency hearing loss (CN VIII), tinnitus, facial motor dysfunction (CN VII), facial sensory dysfunction (CN V), taste disturbance (chorda tympani)
  • signs of posterior fossa mass effect: headache, nausea, vomiting, disequilibrium, ataxia
  • hemifacial spasm, trigeminal neuralgia (tic douloureux)
  • may widen CSF space (cistern) in 25%
  • bone erosion / hyperostosis
  • sharp margination with brain

Types:

  1. benign condition
    1. Vestibular schwannoma (60–90%)
    2. Meningioma (10–18%)
    3. Epidermoid cyst (5–9%)
    4. Nonvestibular schwannoma:
      • trigeminal schwannoma
      • facial schwannoma
      • glossopharyngeal schwannoma
    5. Arachnoid cyst(<1%)
    6. Lipoma (<1%)
    7. Dermoid
    8. Choroid plexus papilloma
    9. Ependymoma
    10. Glomus jugulare tumor
    11. Chordoma
    12. Aneurysm of basilar / vertebral / posterior inferior cerebellar artery
    13. Atherosclerotic dolichoectasia
  2. malignancy
    1. Lymphoma
    2. Melanoma
    3. Metastasis (0.2–2%)
    4. Chondrosarcoma
    5. Exophytic brainstem glioma

mnemonic: Ever Grave CerebelloPontine Angle Masses

  • Epidermoid
  • Glomus jugulare tumor
  • Chondroma, Chordoma, Cholesteatoma
  • Pituitary tumor, Pontine glioma (exophytic)
  • Acoustic + trigeminal schwannoma, Aneurysm of basilar / vertebral artery, Arachnoid cyst
  • Meningioma, Metastasis

 Outline