1. Neuro DDx EC
Persistent embyronic ICA to vertebrobasilar connections: trigeminal (#1), hypoglossal, otic, proatlantic artery
Intraaxial hemorrhage: HTN (#1), tumor, trauma, AVM, aneurysm, coagulopathy, amyloid angiopathy, emboli,
hemorrhagic infarction, vasculitis, HTN encephalopathy (eclampsia, cyclosporine)
Aneurysm: saccular – degenerative, trauma, mycotic, vasculopathies; fusiform – atherosclerotic; dissecting –
trauma > vasculopathy > spontaneous
SAH: aneurysm (#1), trauma, AVM, coagulopathy, extension of intraparenchymal bleed, idiopathic, spinal AVM
Vascular malformations: AVM, capillary telangiectasia, cavernous malformation, venous anomaly, vein of Galen
AVM or varix
Stroke: atherosclerosis, cardiac emboli, arterial dissection, vasculopathy, IVDA, venous thrombosis, blood
dyscrasias
Venous sinus thrombosis: pregnancy, dehydration, infection, tumor, hypercoagulable state, trauma
Primary brain injury: epidural hematoma, SDH, subdural hygroma, DAI, cortical contusion
Secondary brain injury: cerebral herniation, diffuse cerebral edema, arterial dissection (spontaneous, trauma,
HTN, vasculopathy, migraine, IVDA), CCF
Extraaxial masses: hemisphere – meningioma, mets, lymphoma, arachnoid cyst, dermoid/epidermoid,
hemorrhagic or infectious fluid collections, hemangiopericytoma; clivus/prepontine cistern – meningioma, mets,
chordoma, chondrosarcoma; CPA mass – acoustic neuroma, meningioma, mets, epidermoid, petrous apex
cholesterol granuloma, paraganglioma, aneurysm, arachnoid cyst
Intraaxial masses: hemisphere – astrocytoma, GBM, oligodendroglioma, lymphoma, mets, PNET, ganglioglioma,
DNET; sella – adenoma, craniopharyngioma, Rathke’s cyst, mets, abscess, sarcoid, EG stalk; brainstem –
astrocytoma, GBM; pineal region – germinoma, teratoma, pineocytoma, pineoblastoma; cerebellum – astrocytoma,
medulloblastoma, hemangioblastoma, mets, ependymoma, choroid plexus papilloma; temporal lobe in young patient
– ganglioglioma, DNET, JPA, PXA
Multiple lesions: tumor – mets, GBM, lymphoma; infection – abscess, fungus, cysticercosis, toxoplasmosis;
vascular – embolic infarctions, multifocal hemorrhage, DAI, contusions, cavernous hemangiomas, vasculitis
Corpus callosum lesions: tumors – GBM, lymphoma, lipoma, mets (rare); demyelinating – MS, ADEM, PML;
infarct – always also involves cingulate gyrus; trauma - DAI
Intrasellar masses: pituitary adenoma, apoplexy, craniopharyngioma, Rathke’s cyst, mets, aneurysm, abscess
Suprasellar masses: SATCHMOE – sellar lesion extending superiorly, sarcoid, aneurysm, arachnoid cyst,
teratoma, craniopharyngioma, hypothalamic glioma, mets, meningioma, optic nerve glioma, EG,
epidermoid/dermoid; adults – macroadenoma (#1), meningioma, glioma, craniopharyngioma, aneurysm; children –
craniopharyngioma (#1), glioma, germinoma, hypothalamic hamartoma, EG
Posterior fossa tumors: adults – mets, hemangioblastoma, astrocytoma, choroid plexus papilloma, meningioma,
epidermoid, dysplastic gangliocytoma; children -–JPA, medulloblastoma, brainstem glioma, ependymoma
Brain tumor in infant: teratoma (#1), PNET, choroid plexus papilloma, astrocytoma
Intraventricular tumors: adults – astrocytoma, subependymoma, meningioma, mets, cysticercosis; children –
choroid plexus papilloma, ependymoma, medulloblastoma, teratoma, astrocytoma; lateral ventricle – PNET, choroid
plexus papilloma, glioma, JPA, subependymoma, astrocytoma, mets, oligodendroglioma, meningioma, central
neurocytoma; 3rd
ventricle – astrocytoma, EG stalk, germinoma, extrinsic craniopharyngioma, colloid cyst, glioma,
mets, pituitary or pineal mass, aneurysm, sarcoid; 4th
ventricle – ependymoma, medulloblastoma, choroid plexus
papilloma, mets, hemangioblastoma, subependymoma
CPA mass: acoustic neuroma (#1), meningioma, epidermoid, arachnoid cyst, mets, ependymoma through Luschka,
lipoma
Cystic mass: tumor – cystic astrocytoma/GBM, hemangioblastoma, mets, necrotic pituitary adenoma,
craniopharyngioma; benign – epidermoid/dermoid, arachnoid cyst, porencephalic cyst, colloid cyst, cavum variants,
Rathke’s cyst, thrombosed aneurysm
Diffuse infiltrative: lymphoma, gliomatosis cerebri, white matter disease
Restricted diffusion: infarct, infection, possibly subacute hemorrhage
Metastasis: intraaxial – lung, breast, colon, melanoma; extraaxial – breast, lymphoma, prostate, neuroblastoma;
hemorrhagic – melanoma, renal, chorioCA, thyroid
Tumors with CSF seeding: choroid plexus papilloma, ependymoma, PNET (medulloblastoma), piineoblastoma,
germinoma, GBM
Hyperdense lesion on CT: lymphoma, medulloblastoma/PNET, ependymoma, germinoma, GBM, hemorrhagic
mets, mucinous mets, osteogenic tumor, hemorrhage, meningioma, colloid cyst, aneurysm

2. Calcified intraparenchymal lesions: oligodendroglioma, ependymoma, mucinous adenoCA, osteogenic sarcoma,
toxoplasmosis, CMV, cysticercosis, TB, AVM, aneurysm, TS, Sturge-Weber, hematoma; sellar lesions –
meningioma, craniopharyngioma, germ cell tumor, aneurysm
T2 hypointense lesions: ferritin, hemosiderin, deoxyhemoglobin, intracellular methemoglobin, melanin,
calcification, lymphoma, myeloma, neuroblastoma, fibrous tissue (meningioma), high protein concentration, flow
void
T1 hyperintense lesions: Gd, methemoglobin, melanin, certain states of calcium, fat (dermoid), high protein
concentration (colloid cyst), slow flow
Lesions with no enhancement: cysts, tumors with intact BBB (low-grade gliomas)
Lesions with strong enhancement: meningioma, medulloblastoma/PNET, AVM, paraganglioma, aneurysm, HIV-
associated lymphoma, GBM
Ring enhancement: mets, abscess, GBM, infarct, contusion, AIDS, lymphoma, demyelinating, resolving
hematoma, radiation
Diffuse meningeal enhancement: meningitis, carcinomatosis (lymphoma, mets), post-op, SAH, intracranial
hypotension, CSF leak
Basilar meningeal enhancement: infection - TB (#1), fungal, pyogenic (more common on convexity),
cysticercosis; tumor – lymphoma, leukemia, carcinomatosis; inflammatory – sarcoid, rheumatoid pachymeningitis,
drugs, pantopaque, ruptured dermoid
Ependymal enhancement: tumor – lymphoma, mets, CSF seeding (PNET, GBM); infection – spread of
meningitis, CMV (rare); inflammatory ventriculitis – postshunt or after instrumentation, posthemorrhage
T2 hypointense basal ganglia lesions: old age, any chronic degenerative disease (MS, Parkinson’s), childhood
hypoxia
T2 hyperintense basal ganglia lesions: tumor – lymphoma, NF; ischemia – hypoxic encephalopathy, venous
infarction; neurodegenerative diseases (uncommon), Leigh’s dz; toxin – CO, CN, H2S poisoning, hypoglycemia,
methanol; infection – Cryptococcus, parasites
T1 hyperintense basal ganglia lesions: dystrophic calcifications (any cause), hepatic failure, NF, manganese
Basal ganglia calcification: physiologic (#1), hypoparathyroid, HPT, TORCH, AIDS, TB, toxoplasmosis,
cysticercosis (common), lead, CO, radiation, chemotherapy, Fahr’s disease, mitochondrial (common), ischemic-
hypoxic injury
White matter disease: demyelinating (MS, ADEM, CPM), dysmyelinating (leukodystrophies), tumor (lymphoma,
mets) vasculopathies (small vessel ischemic dz, vasculitis, HTN, eclampsia, migraines, radiation, chemotherapy,
cyclosporine, IVDA), inflammatory (Lyme, sarcoid, HIV, PML, CMV)
Wallerian degeneration: infarction, trauma, demyelinating, radiation, neurodegenerative, tumor
Neurodegenerative disorders: WM – demyelinating, dysmyelinating; GM – Alzheimer’s, Pick’s, multiinfarct
dementia, Parkinson’s, lysosomal storage disorders, Wernicke’s, Creutzfeldt-Jakob, mesial temporal sclerosis; BG –
Huntington’s, Wilson’s, Fahr’s, Leigh’s, ALS
Cerebellar atrophy: oligopontocerebellar degeneration, alcohol, dilantin, hemosiderin deposition
Noncommunicating hydrocephalus: Foramen of Monro obstruction – 3rd
ventricle tumors, colloid cyst,
oligodendroglioma, central neurocytoma, giant cell astrocytoma in TS, ependymoma, suprasellar tumors; aqueduct
obstruction – congenital aqueductal stenosis, ventriculitis, IVH, tumor (mesencephalic, pineal, posterior 3rd
ventricle
region); 4th
ventricle obstruction – DW malformation, IVH, infection, subependymoma, exophytic brainstem glioma,
posterior fossa tumors
Communicating hydrocephalus: meningitis (infectious, carcinomatous), SAH, surgery, venous thrombosis; NPH
Cystic supratentorial congenital anomalies: holoprosencephaly, hydrancephaly, aqueductal stenosis, callosal
dysgenesis, porencephaly, arachnoid cyst, cystic teratoma, epidermoid/dermoid, vein of Galen AVM
Posterior fossa cystic abnormalities: DW malformation (vermian hypoplasia/aplasia and large posterior fossa),
DW variant (normal size posterior fossa and vermian hypoplasia), megacisterna magna (normal vermis),
retrocerebellar arachnoid cyst (must show mass effect), Chiari 4 (near complete absence of cerebellum),
epidermoid/dermoid, cystic tumor, Joubert’s syndrome (superior vermian hypoplasia/aplasia),
rhomboencephalosynapsis (vermian hypoplasia/aplasia + fusion)
Absent septum pellucidum: holoprosencephaly, ACC, septooptic dysplasia, Chiari 2
Migration and sulcation anomalies: lissencephaly, schizencephaly, polymicrogyria, pachygyria, cortical
heterotopia (focal, diffuse, subependymal), hemimegalencephaly
Phakomatoses: NF, TS, VHL, Sturge-Weber
Diffuse marrow involvement: mets, myeloma, lymphoma, leukemia, anemia, Paget’s, FD

3. Spine DDx
Spinal cord compression: criteria – no CSF seen around cord, narrowed AP diameter of cord (<7mm), deformity
of cord; causes – infection (TB, pyogenic), compression fracture (CA, trauma), spondylosis and disk disease
(herniated nucleus, hypertrophy of ligaments, osteophyte, facet hypertrophy), primary bone disorders (Paget’s),
epidural hematoma
Intramedullary lesions: astrocytoma (#1), ependymoma (#2), hemangioblastoma, lymphoma, mets (rare),
demyelinating disease/myelitis, syrinx, AVM, trauma (contusion), radiation, sarcoid, infection (rare), infarction
Intradural extramedullary lesions: nerve sheath tumor (#1), meningioma, drop mets, lipoma, teratomatous lesion,
arachnoid cyst, arachnoiditis/meningitis, AVM/AVF, ependymoma, sequestered disc fragment, lymphoma, sarcoid,
pantopaque
Extradural lesions: disc disease, mets, lymphoma, epidural abscess, epidural hematoma, lipomatosis (thoracic),
synovial cyst, extramedullary hematopoiesis, Tarlov cyst, discitis/osteomyelitis, spondylolysis, RA
Syrinx: primary – Chiari malformations, spinal dysraphism, DW, diastematomyelia; acquired – tumor
(astrocytoma, ependymoma), trauma (spinal cord injury, vascular insult), inflammatory (arachnoiditis/meningitis,
SAH)
Head and Neck DDx
External auditory canal: exostoses, malignant otitis externa, atresia
Clivus mass: chordoma, chondrosarcoma, plasmacytoma, mets, lymphoma, FD, EG
Petrous apex mass: cholesterol granuloma, mucocele, petrous apicitis, epidermoid, mets, myeloma,
chondrosarcoma, meningioma, aneurysm
Soft tissue mass in middle ear: cholesteatoma, cholesterol granuloma, glomus tympanicum tumor, aberrant ICA,
high or dehiscent jugular bulb
Intracanalicular IAC masses: exclusively intracanalicular – acoustic neuroma, facial neuroma, hemangioma,
lipoma; not primarily intracanalicular – meningioma, epidermoid
Hearing loss: conductive – otitis media, cholesteatoma, otosclerosis, trauma (longitudinal fracture); sensorineural –
idiopathic hereditary, acoustic neuroma, trauma (transverse fracture)
Pulsatile tinnitus: aberrant ICA, jugular bulb anomalies, glomus jugulare, glomus tympanicum, AVM, ICA
aneurysm at petrous apex
Jugular fossa mass: glomus jugulare (#1), NF (#2), schwannoma, chondrosarcoma, mets
Orbital masses by etiology: tumors – hemangioma (adults: cavernous; children: capillary), lymphoma, mets
(neuroblastoma, breast), lymphangioma, rhabdomyosarcoma, hemangiopericytoma, neurofibroma; inflammatory –
pseudotumor, thyroid ophthalmopathy, cellulitis, abscess, Wegener’s; vascular – carotid-cavernous fistula, venous
varix, thrombosis of superior ophthalmic vein; trauma – hematoma, FB, lens dislocation
Extraconal disease: nasal disease – infection, neoplasm; orbital bone disease – subperiosteal abscess,
osteomyelitis, FD, tumors, trauma; sinus disease – mucocele, invasive infections, neoplasm; lacrimal gland disease –
adenitis, lymphoma, pseudotumor, tumor
Intraconal disease: well-defined margins – hemangioma, schwannoma, orbital varix, meningioma; ill-defined
margins – pseudotumor, infection, lymphoma, mets; muscle enlargement – pseudotumor, Graves’, myositis, carotid-
cavernous fistula
Vascular orbital lesions: tumor – hemangioma, lymphangioma, hemangioendothelioma, hemangiopericytoma,
meningioma, hypervascular mets; vascular (with enlarged superior ophthalmic vein) – carotid cavernous fistula,
cavernous thrombosis, orbital varix, ophthalmic artery aneurysm
Optic neuritis: abnormal T2 signal and enhancement but not enlarged – MS, sarcoid, infection
Optic neuropathy: abnormal T2 signal only – compression, ischemia, pharmacologic, toxins, trauma
Optic nerve tumor: abnormal T2 signal and enhancement and nerve enlarged – glioma, meningioma
Optic nerve sheath enlargement: tumor – optic nerve glioma, meningioma, meningeal carcinomatosis, mets,
lymphoma, leukemia; inflammatory – optic neuritis, pseudotumor, sarcoid; increased intracranial pressure; trauma –
hematoma
Tramtrack enhancement of orbital nerve: optic nerve meningioma, optic neuritis, idiopathic, pseudotumor,
sarcoid, lymphoma, leukemia, perioptic hemorrhage, mets, normal variant
Ocular muscle enlargement: thyroid ophthalmopathy (#1, painless), pseudotumor (painful), infection from
adjacent sinus, TB, sarcoid, carotid cavernous fistula, hemorrhage, tumor

4. Childhood orbital masses: retinoblastoma, rhabdomyosarcoma, optic nerve glioma, lymphoma, leukemia,
hemangioma, lymphangioma, dermoid, neuroblastoma
Adult orbital masses: hemangioma, schwannoma, melanoma, meningioma, lymphoma, pseudotumor, trauma
Cystic orbital lesions: dermoid, epidermoid, teratoma, ABC, cholesterol granuloma, colobomatous cyst
T1 hyperintense orbital masses: tumor – melanoma, retinoblastoma, choroidal mets, hemangioma; detachment –
Coat’s disease, persistent hyperplastic primary vitreous, trauma; other – hemorrhage, phthisis bulbi
Globe calcifications: tumor – retinoblastoma (95%), astrocytic hamartoma (TS, NF), choroidal osteoma; infection
(chorioretinitis) – toxoplasmosis, herpes, CMV, rubella; other – phthisis bulbi (calcification in endstage disease,
shrunken bulb), optic nerve drusen (most common cause of calcifications in adults, bilateral)
Micropthalmia: persistent hyperplastic primary vitreous, retinopathy of prematurity, congenital rubella, phthisis
bulbi
Sudden onset proptosis: orbital varix, hemorrhage into cavernous hemangioma or lymphangioma, CCF,
thrombosis of superior orbital vein
Lacrimal gland enlargement: benign lymphoid hyperplasia, pseudotumor, sarcoid, Sjogren syndrome,
pleomorphic adenoma, adenoid cystic CA, lymphoma, leukemia, dacryoadenitis
Diffuse bone abnormality: FD, Paget’s, thalassemia, osteopetrosis, craniometaphyseal dysplasia, mets
Radioopaque sinus: normal variant – hypoplasia, unilateral thick bone; sinusitis (acute: AFL; chronic: mucosal
thickening, retention cysts) – allergic, aspergillosus, mucor, sarcoid, Wegener’s; solid masses – SCC, polyp,
inverted papilloma, lymphoma, juvenile angiofibroma (most common tumor in children), mucocele (expansile,
associated with CF in children), esthesioneuroblastoma, mets, osteoma, FD; postsurgical – Caldwell-Luc
Mucosal space mass: SCC, lymphoma, rhabdomyosarcoma, melanoma, adenoids, juvenile angiofibroma,
Thornwald’s cyst
Parapharyngeal and carotid space masses: salivary gland tumors (80% benign), vagal schwannoma, cervical
sympathetic plexus schwannoma, glomus vagale, nasopharyngeal CA, lymphadenopathy, abscess, cellulitis
Prevertebral mass: mets, chordoma, osteomyelitis, abscess, hematoma
Sublingual space mass: lymphangioma, ranula, hemangioma, lingual thyroid, inflammatory
Simultaneous sublingual and submandibular space mass: diving ranula, lymphangioma, abscess
Post-styloid parapharyngeal mass: salivary tissue, nerves, nodes, glomus tumor
Prestyloid parapharyngeal mass: pleomorphic adenoma, Warthin’s, mucoepidermoid, adenoid cystic, branchial
cleft cyst, neurogenic tumor, hemangioma, node
Bilateral parotid low attenuation lesions: HIV lymphoepithelial cysts, Sjogren’s, Warthin’s tumor, infection
Enlarged parotids: obesity, DM, alcohol, cirrhosis, malnutrition, drugs
Sialoliths: sarcoid, Sjogren’s, HPT
Cystic extrathyroid lesions: neck – branchial cleft cyst (lat to carotid), thyroglossal duct cyst (midline mass),
ranula (retention cyst of sublingual glands), retention cysts of mucous glands (parotid), cystic hygroma
(lymphangioma, most common < 2y/o); nasooropharnyx – Thornwald’s cyst, mucus retention cyst, necrotic SCC;
larynx, paralaryngeal space – laryngocele, mucus retention cyst
Cystic thyroid lesions: colloid cyst, cystic degeneration, cystic papillary tumor, cystic mets
Bilateral thyroid masses: lymphoma, mets (RCC, lung), multiple primary tumors, MNG, thyroiditis, cysts
Neck lymphadenopathy: enlarged Waldeyer’s ring – lymphoma, mononucleosis, HIV; skin lesions – KS, sarcoid,
lymphoma, CA, cat-scratch, TB, Actinomycosis; enlarged nodular salivary glands – HIV, Sjogren, sarcoid,
lymphoma, cat-scratch; calcified – thyroid CA, treated lymphoma, sarcoid, silicosis, TB
Solid neck mass: SCC of larynx or nasooropharynx, lymphadenopathy, parotid tumor, neurofibroma, glomus
tumor, dermoid, teratoma, infection, granulomatous inflammation, ectopic thyroid
Vascular head and neck mass: glomus tumor – carotid body, vagale, jugulare, tympanicum; hemangioma; AVM;
aneurysm (often ICA) – pseudoaneurysm, posttraumatic
Vocal cord paralysis: tumor, post-op, iatrogenic, idiopathic
AIDS: ENT complications in 50%; parotid – multiple intraparotid cystic masses (benign lymphoepithelial lesion),
lymphadenopathy; sinonasal – sinusitis, KS; oral cavity – Candida, periodontal an gingival infections;
pharynx/larynx – opportunistic infections, epiglottitis, lymphoma; temporal bone (rare) – otitis media, otitis externa
Odontogenic: cysts, ameloblastoma, odontogenic carcinoma or sarcoma; nonodontogenic – osteosarcoma,
chondrosarcoma, Ewing’s, myeloma