▶️Low T2 signal (less cytoplasm and more nucleus so less water in cells and lower T2 signal)
▶️Hyperdensity on CT
▶️Periventricular location
Hypercellular tumor continued
▶️Glioblastoma or high grade glioma
Variable but may have more eccentric or nodular restriction around areas of necrosis and heterogeneous enhancement
4️⃣HEMATOMA
RBCs trapped in serum and fibrin can restrict on DWI (though blood can also be dark on DWI from susceptibility)
Hyperdensity on CT is a giveaway but this may fade overtime or you may not have a CT
Look for a rim of HYPERINTENSITY ON T1 and HYPOINTENSITY on SWI
5️⃣DEMYELINATION
High signal on DWI is predominantly due to T2 SHINE THROUGH
True restriction may be seen at the LEADING EDGE (along the margin) in acute demyelination possibly from cytotoxic edema, reduced fiber tract organization, or myelin fragments
(This example is PML)
6️⃣EPIDERMOID CYST
Tightly organized epithelial layers cause a light bulb bright restriction
ADC tends to be ISOINTENSE TO BRAIN PARENCHYMA (not super dark), possibly from movement of fluid between layers (at least that’s how I think of it)
Epidermoid cyst continued
▶️CSF intensity on T1 & T2
▶️Dirty on FLAIR
▶️DO NOT ENHANCE! (May have a tiny rim of enhancement along edge but NO CENTRAL)
Bonus cases
7️⃣SEIZURE
Shows gyriform or cortical restricted diffusion (often in the mesial temporal lobe)
Examples in 2 different patients
8️⃣ENCEPHALITIS
Diffusion restriction in the insula and temporal lobes favors herpes encephalitis, though any encephalitis can cause restriction
Herpes is usually bilateral but asymmetric and may have patchy enhancement and hemorrhage
Case of herpes
9️⃣CJD
Diffusion restriction is seen in the basal ganglia, thalami, and cortex. This can be asymmetric
🔟Many Toxic/metabolic disorders
Hepatic encephalopathy
Acute toxic leukoencephalopathy
Hypoxia
Methotrexate toxicity
Drug abuse
CO poisoning
Many more
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⭐️ Answer: petrous apicitis complicated by brainstem abscess
🔷Petrous apicitis can display the clinical triad of Gradenigo’s syndrome
1️⃣Otorrhea
2️⃣Cranial nerve 6 palsy
3️⃣Pain in distribution of trigeminal nerve
▶️Petrous apicitis usually occurs as a complication of otomastoiditis when the infection spreads to the skull base.
▶️The petrous apex is in close proximity to Dorello’s canal (where cranial nerve 6 runs through) and Meckel’s cave (where the trigeminal ganglion is located)
▶️CVT causes retrograde venous pressure leading to focal vasogenic edema
▶️Increased back pressure is characterized by dilated veins and petechial hemorrhage which can progress to large hematomas and ischemic neurological damage
🔷Two types of edema can develop:
1️⃣Vasogenic (from venous back pressure)
2️⃣Cytotoxic (ischemia)
🔷Risk factors:
💡 Up to 20% are idiopathic
1️⃣Trauma
2️⃣Tumor/malignancy (compression/invasion from meningioma)
3️⃣Infection
4️⃣Hormonal (pregnancy)
5️⃣Dehydration
🔷What is the most likely diagnosis in this 70 y/o F who lives with feral cats presenting w/ vomiting, diarrhea, leukocytosis, fever for 3 days and progressive decline in level of consciousness?
🔷CSF: initially normal, repeat a few days later ⬆️ WBC (lymphocyte predominant), ⬆️ Protein, normal glucose
🔷 South Central Asia and Southeast Asia appear to have the greatest number of cases
🔷Dogs are the most common reservoir 🐶 (bats in developed countries🦇)
🔷CLINICAL:
▶️Incubation period typically 3 weeks to 2 months (range 5 days to 6 months)
▶️Prodromal symptoms: fever, malaise, anxiety,
and itching at the inoculation site
💡Once in the body, the virus begins retrograde flow to extend to the dorsal root ganglion, which may correlate with neuropathic pain
▶️CNS manifestations: Mental status changes of excessive agitation and depression with hydrophobia and aerophobia
🔷35 y/o F w/ history of Li Fraumeni syndrome presents w/ intermittent left sided weakness and pain. The feeling is of heaviness, difficulty w/ grip, dropping objects and frequent falls. Episodes last for weeks to months. What is your diagnosis? 🧠
🎉Congrats to all the rad fellow matches today!!! 🍾
⭐️ Answer: Tumefactive demyelination (MS in this case)
🔷Imaging in this case is specific enough to diagnosis with confidence but we need extra caution in patients with genetic predisposition to malignancy
💡 In cases where imaging or clinical picture are atypical or discordant for demyelination (especially if there is a genetic disorder), it is best to refer to neurology for proper work up, possible trial of steroids and short imaging follow up
🚩 Be suspicious against MS if your patient has:
1️⃣Systemic symptoms (fever, weight loss, joint or skin symptoms, etc.)
2️⃣Seizures, hearing loss, meningitis signs, movement disorder, aphasia
3️⃣”Family history”
4️⃣Age (<20 or >50)
5️⃣Lesions are symmetric
6️⃣Hemorrhage or dense on CT
7️⃣Diffusion restriction other than leading edge
8️⃣Strokes
9️⃣Cysts
🔟Cortical infiltration
⭐️ 30 y/o presents w/ R sided weakness & fall. Pt had a recent admission ~4 months ago for headache, AMS, seizure & diplopia. Clinically stable until now.