Neuroradiology Flashcards
Around 95% of hyperacute infarcts (< 6 hours) show diffusion restriction on DWI, with hyperintensity on DWI and corresponding hypointensity on ADC maps. The hyperintensity on DWI is due to cytotoxic edema.
Around 95% of hyperacute infarcts (< 6 hours) show diffusion restriction on DWI, with hyperintensity on DWI and corresponding hypointensity on ADC maps. The hyperintensity on DWI is due to cytotoxic edema.
Approximately 10% of large MCA occlusions progress to significant edema, herniation, and may need early decompressive hemicraniectomy.
Approximately 10% of large MCA occlusions progress to significant edema, herniation, and may need early decompressive hemicraniectomy.
Posterior cerebral artery (PCA) primarily supplies the occipital and inferior temporal lobes as well as the thalamus, hypothalamus, geniculate bodies, posterior limb of internal capsule, upper midbrain, and choroid plexus. CTA or MRA may be performed to evaluate for vessel occlusion. It should be remembered that the posterior communicating artery allows emboli from both anterior and posterior circulation to affect PCA distribution.
Posterior cerebral artery (PCA) primarily supplies the occipital and inferior temporal lobes as well as the thalamus, hypothalamus, geniculate bodies, posterior limb of internal capsule, upper midbrain, and choroid plexus. CTA or MRA may be performed to evaluate for vessel occlusion. It should be remembered that the posterior communicating artery allows emboli from both anterior and posterior circulation to affect PCA distribution.
Subacute infarction is approximately 2-14 days following the initial ischemic event. Hemorrhagic transformation of ischemic infarction occurs in 15-20 % of cases
Subacute infarction is approximately 2-14 days following the initial ischemic event. Hemorrhagic transformation of ischemic infarction occurs in 15-20 % of cases
Coronal images best demonstrate the anatomy of the ostiomeatal unit (OMU). CECT is usually reserved for complicated cases in which soft tissue abscess, neoplasm, or vascular complication (cavernous sinus thrombosis) is suspected.
Coronal images best demonstrate the anatomy of the ostiomeatal unit (OMU). CECT is usually reserved for complicated cases in which soft tissue abscess, neoplasm, or vascular complication (cavernous sinus thrombosis) is suspected.
Sagittal reformatted images are helpful for delineating frontal recess (FR) and the sphenoethmoid region anatomy.
MR imaging protocols generally include axial and coronal T1, STIR, and T1 C+ images, typically with fat suppression.
Angiography is rarely needed for diagnostic purposes but may be performed for intervention prior to resection of vascular neoplasms or for treatment of epistaxis.
Sagittal reformatted images are helpful for delineating frontal recess (FR) and the sphenoethmoid region anatomy.
MR imaging protocols generally include axial and coronal T1, STIR, and T1 C+ images, typically with fat suppression.
Angiography is rarely needed for diagnostic purposes but may be performed for intervention prior to resection of vascular neoplasms or for treatment of epistaxis.
The extraaxial optic pathways can be segmented (posterior to anterior) into the optic tract, optic chiasm, cisternal nerve, intracanalicular nerve, and intraorbital nerve. The optic sheath is a dural reflection that is contiguous with intracranial dura mater. Optic glioma, optic melanoma, and retinoblastoma may all follow the orbital segment of the optic nerve to reach intracranial structures.
The extraaxial optic pathways can be segmented (posterior to anterior) into the optic tract, optic chiasm, cisternal nerve, intracanalicular nerve, and intraorbital nerve. The optic sheath is a dural reflection that is contiguous with intracranial dura mater. Optic glioma, optic melanoma, and retinoblastoma may all follow the orbital segment of the optic nerve to reach intracranial structures.
T1 C+ FS MR demonstrates normal enhancement of the extraocular muscles. The optic nerve itself should not demonstrate intrinsic enhancement. Normally, the optic nerve sheath dura can demonstrate subtle enhancement.
T1 C+ FS MR demonstrates normal enhancement of the extraocular muscles. The optic nerve itself should not demonstrate intrinsic enhancement. Normally, the optic nerve sheath dura can demonstrate subtle enhancement.
Orbital Cavernous Hemangioma
Venous vascular malformation of orbit characterized by endothelial-lined cavernous spaces
Pseudo-encapsulated morphology distinguishes orbital cavernous venous malformation from venous malformations elsewhere in the head & neck
Synonymous with cavernous “hemangioma” (misnomer)
Virtually all retinoblastomas demonstrate hypointensity relative to vitreous on T2WI; the lenticular shape is typical for early lesions.
Virtually all retinoblastomas demonstrate hypointensity relative to vitreous on T2WI; the lenticular shape is typical for early lesions.
Sinonasal Mucocele
Imaging
Opacified, expanded sinus with smooth remodeling of walls
May occur in septated sinuses & pneumatized anatomic variant air cells
Frontal (60-65%) > ethmoid (25%) > maxillary (5-10%) > sphenoid (2-5%)
CT: Thin-section CT with coronal & sagittal reformat helpful for surgical planning and delineation of adjacent normal anatomy
Low-density or soft tissue density opacification of sinus with expansion
Bony sinus walls remodeled
No central enhancement; ± minimal peripheral enhancement
MR: Enhanced MR recommended for detection of intracranial involvement & identifying potential obstructing neoplasm as underlying cause
High water content mucus typically shows ↓ T1 signal, ↑ T2 signal, but signal varies with protein content
The collar sign and the fallen viscus sign are signs of diaphragmatic traumatic injury
The collar sign and the fallen viscus sign are signs of diaphragmatic traumatic injury
Closed loop obstruction
SB segments are markedly distended (> 4 cm) by fluid, little gas
Whirl sign due to tightly twisted mesenteric vessels
“Balloons-on-strings”: Dilated SB tethered by stretched mesenteric vessels
Strangulating SBO: Impaired blood supply to SB
Absent, decreased, or delayed bowel wall enhancement
Bowel wall thickening (edema or hemorrhage)
Mesenteric and interloop edema ± ascites
Vessels: Congested, thrombosed, or obscured
Obscured margins among affected SB segments
Closed loop obstruction
SB segments are markedly distended (> 4 cm) by fluid, little gas
Whirl sign due to tightly twisted mesenteric vessels
“Balloons-on-strings”: Dilated SB tethered by stretched mesenteric vessels
Strangulating SBO: Impaired blood supply to SB
Absent, decreased, or delayed bowel wall enhancement
Bowel wall thickening (edema or hemorrhage)
Mesenteric and interloop edema ± ascites
Vessels: Congested, thrombosed, or obscured
Obscured margins among affected SB segments
string-of-pearls sign , indicating gas within fluid-distended, obstructed segments of SB.
string-of-pearls sign , indicating gas within fluid-distended, obstructed segments of SB.
The SB is markedly distended with a small bowel feces sign in the distal ileum . This is a classic example of DIOS (distal intestinal obstruction syndrome) in a patient with cystic
The SB is markedly distended with a small bowel feces sign in the distal ileum . This is a classic example of DIOS (distal intestinal obstruction syndrome) in a patient with cystic
