Neurologic Imaging
| atherosCLerotiC disease | Slim sign: collapse of ICA above
stenosis atherosCLerotiC disease |
| atherosCLerotiC disease | Color Doppler flow imaging of
carotid arteries • High-grade stenosis with minimal flow (string sign in angiography) is detected more reliably than with conventional Doppler US. CT • To determine complete occlusion versus a string sign (near but not complete occlusion), delayed images must be obtained immediately after the initial contrast images. |
| Bifid post-CS sign (85%) | Bifid post-CS sign (85%) |
| cap sign | • T2W: hyperintense. 20%-33% of ependymomas demonstrate the “cap sign,” a rim of extreme hypointensity (hemosiderin) seen at the poles of the tumor on T2W images. Most cases (60%) also show evidence of cord edema around the masses. |
| Classification
of Plain Radiographic Abnormalities of the Infant Skull |
Variations in skull
density Decreased density: generalized or localized Increased density: generalized or localized Variations in skull size Decreased size (microcephaly) Increased size (macrocephaly) Abnormal head shape Calvarial defects Acquired conditions Posttraumatic abnormalities Neoplasia |
| delta sign | Primary (sinus occlusion) • Clot in sinus is hyperdense on noncontrast CT and hypodense on contrast-enhanced CT. • Dural enhancement of sinus margin: delta sign • MRI Bright sinus on T1W and T2W (depending on stage) Absence of flow void • Pearl: If bilateral thalamic infarcts or infarcts do not conform to an arterial territory, suspect venous thrombosis. venous sinus thrombosis |
| dense MCA sign | Early CT signs of cerebral
infarction include: Loss of gray-white interfaces (insular ribbon sign) Sulcal effacement Hyperdense clot in artery on noncontrast CT (dense MCA sign) |
| empty thecal sac sign | • Clumping of nerve roots within
the thecal sac (intrathecal pseudomass); blunting of caudal nerve root sleeves; nerve roots may also clump peripherally (empty thecal sac sign) |
| eye of tiger sign | Hallervorden-Spatz disease (eye
of tiger sign — gliosis (white) surrounded by iron deposit (black) on T2W
images) t2w hyperintense basaL gangLia Lesions |
| Hot cross bun sign | • “Hot cross bun” sign in the
pons on axial T2/FLAIR parkinson pLus syndromes (patients who respond poorLy to antiparkinson's mediCation) Multisystem Atrophy (MSA) |
| Hummingbird sign | Volume loss of the midbrain —
Hummingbird sign Progressive Supranuclear Palsy (PSP) |
| Insular ribbon sign | Early CT signs of cerebral
infarction include: Loss of gray-white interfaces (insular ribbon sign) Sulcal effacement Hyperdense clot in artery on noncontrast CT (dense MCA sign) |
| Intraparietal sulcus intersects the post-CS (99%) | Intraparietal sulcus intersects the post-CS (99%) |
| Ivy sign | • MRI: multiple tiny flow voids on T2W images, which are collaterals; engorged collaterals may produce FLAIR bright sulci (Ivy sign) |
| large lipid peak | • Sign suggesting metastasis over primary brain tumor: large lipid peak |
| Leptomeninges insinuate into cerebral sulci | Leptomeninges insinuate into
cerebral sulci, which is a sign that helps distinguish a leptomeningeal process from a dural one. Carcinomatous meningitis Leptomeningeal metastases are more common than dural metastases, although the two may coexist. • Common primary neoplasms that cause carcinomatous meningitis include breast, lung, and skin (melanoma). • MRI is more sensitive than CT for detection. • Leptomeninges insinuate into cerebral sulci, which is a sign that helps distinguish a leptomeningeal process from a dural one. • Subarachnoid tumor may be detected early by careful examination of cisternal segment of CN V and intracanalicular segment of CNs VII and VIII |
| Macrocephaly | Hydrocephalus Subdural fluid collection Neurofibromatosis Achondroplasia Tuberous sclerosis Metabolic storage disease Alexander disease, Canavan disease Sotos syndrome |
| Mickey Mouse ears” | Ballooning of temporal horns
(“Mickey Mouse ears”) is a sensitive sign. nOnCOmmuniCating hyDrOCephaluS |
| Microcephaly | Causes of Microcephaly Severe hypoxic-ischemic injury Trisomy 21 Trisomy 13 Fetal alcohol syndrome TORCH* syndrome Rubinstein-Taybi syndrome Seckel dwarfism |
| Midline sulcus sign (70%) | Midline sulcus sign (70%) • Most prominent convexity sulcus that reaches the midline is the CS. |
| MRA string sign | Arterial dissection • CTA is preferred first study of choice—see intimal flap and caliber change • MRI/MRA can also be performed. T1W bright hematoma in vessel wall (sequence: T1W with fat saturation): must be interpreted in conjunction with MRA MRA string sign |
| Neptune's trident sign | Trigeminal artery: cavernous ICA to basilar artery (most common), Neptune's trident sign on angiography |
| Neuroparenchymal Involvement in osteogenesis imperfecta | Intracranial hemorrhages are attributed to the development of moyamoya disease with subsequent subarachnoid hemorrhage as well as to vertebral artery damage, vascular fragility, spontaneous intracranial hypotension, and friction between multiple bone fragments in the skull |
| Pars bracket sign (96%) | Pars bracket sign (96%) • Paired pars marginalis at or behind the CS |
| Sigmoidal hook sign | Sigmoidal hook sign
(89%-98%) • Hooklike configuration of the central sulcus corresponding to the motor hand area |
| Signet sign | Signet sign: eccentric vessel
lumen with surrounding thrombus Giant aneurysm |
| Sulcus/pre-CS sign | Superior frontal sulcus/pre-CS
sign (85% specific) • The posterior end of the superior frontal sulcus joins the pre-CS |
| Thin post-central gyrus sign (98%) | Thin post-central gyrus sign (98%) |
| toothpaste sign | MRI Extruded disk material gives
rise to the toothpaste sign (disk material is extruded from disk into the
spinal canal like toothpaste); the material may be continuous with the disk
(simple herniation) or be separated (free fragment herniation). Posterior disk herniation |
| tramtrack sign” | • Linear bands of enhancement
(nerve within tumor): “tramtrack sign” optiC nerve MeningioMa |
| vacuum sign | Plain films • The diagnosis of herniation is not possible by plain film. • All findings of degenerative joint disease (e.g., narrowing of disk space, spurring, eburnation, vacuum sign) may appear in patients with or without herniation. Posterior disk herniation |
| White cerebellum sign | • White cerebellum sign: sparing
of brainstem in comparison with hemispheres diFFuse CerebraL edema |
