Neuroradiology for Medical Students

Neuroradiology for Medical Students

By the end of this tutorial, you will be able to recognize some of the common radiologic problems most often seen by physicians. Hopefully, you will also become more aware of what tests to order and when to order them. We also hope that you will have a little fun in the process!

CT Anatomy (you kind of need to know this)
A = Frontal sinus B = Orbit C = Frontal lobe D = Sphenoid sinus E = Temporal lobe F = External auditory canal G = Mastoid air cells H = Cerebellar tonsil I = Foramen magnum

A = Frontal lobe B = Sylvian fissure C = Temporal lobe D = Temporal horn of the lateral ventricle E = Midbrain F = Ambient cistern G = Fourth ventricle H = Cerebellar hemisphere

A = Falx B = Frontal horn of the lateral ventricle C = Caudate nucleus D = Internal capsule (anterior limb) E = Sylvian fissure F = Basal ganglia G = Third ventricle H = Quadrigeminal plate cistern I = Cerebellum

A = Interhemispheric fissure
B = Genu of the corpus callosum C = Frontal horn of the lateral ventricle D = Internal capsule E = Thalamus F = Pineal gland (calcified) G = Cerebellar vermis H = Straight sinus

A = Falx cerebri B = Frontal lobe C = Parietal lobe D = Body of the lateral ventricle E = Occipital lobe

A = Falx cerebri B = Sulcus C = Gyrus D = Central sulcus E = Superior sagittal sinus

MRI Anatomy (this is kind of really important too)
A = Internal carotid artery B = Medulla C = Cerebellar hemisphere D = Maxillary sinus E = Sigmoid sinus F = External auditory canal

A = Sphenoid sinus B = Internal carotid artery C = Temporal lobe D = Fourth ventricle E = Basilar artery F = Pons G = Middle cerebellar peduncle H = Cerebellum

A = Orbit B = Optic chiasm C = Hippocampal formation D = Cerebral peduncle E = Tegmentum (midbrain) F = Cerebral aqueduct G = Tectum (midbrain) H = Quadrigeminal cistern I = Occipital lobe

A = Caudate nucleus B = Anterior limb of the internal capsule C = Putamen D = Fornix E = Posterior limb of the internal capsule F = Insula G = Thalamus H = Lateral ventricle (posterior horn) I = Corpus callosum (splenium)

A = Lateral ventricle B = Caudate nucleus C = Septum pellucidum D = Sylvian fissure E = Corpus callosum (genu) F = Gray matter G = White matter

Coronal MRI Anatomy A = Intrahemispheric fissure B = Corpus callosum
C = Lateral ventricle D = Suprasellar cistern E = Temporal lobe F = Insular cortex G = Sylvian fissure

A = Superior sagittal sinus
B = Corpus callosum C = Septum pellucidum D = Lateral ventricle E = Caudate nucleus F = Internal capsule G = Interventricular foramen of Monro H = Third ventricle I = Insular cortex

A = Corpus callosum (splenium)
B = Choroid plexus of the lateral ventricle C = Hippocampal formation D = Quadrigeminal cistern E = Fourth ventricle F = Cerebellar hemisphere G = Tentorium cerebelli

Sagittal MRI Anatomy A = Corpus callosum B = Fornix C = Thalamus
D = Optic chiasm E = Pituitary gland F = Pons G = Dens (C2 vertebra) H = Spinal cord I = Pineal gland J = Tectum (midbrain) K = Cerebral aqueduct L = Tegmentum (midbrain) M = Fourth ventricle N = Medulla

Circle of Willis A = Basilar artery B = Posterior cerebral artery
C = Thalamoperforators D = Posterior communicating artery E = Internal carotid artery F = Middle cerebral artery G = Anterior cerebral artery H = Anterior communicating artery

Vascular Territories A = Anterior cerebral artery
B = Middle cerebral artery C = Posterior cerebral artery D = Lenticulostriate arteries

A 82 y/o female presents with sudden onset of right-sided weakness and garbled speech for 3 hours. What, if any, radiologic test would you order, and why? Read about the following imaging techniques to help you formulate an answer:

Imaging Techniques

CT vs. MRI: What to order? MRI CT Acute neurological events:
Stroke Trauma Worst HA of life Acute mental status change First seizure Neurosurgery immediate post-op Follow up: Acute infarcts Hemorrhage Hydrocephalus MRI Acute (usually after CT): Stroke Encephalitis Subacute and chronic: Progressive, subacute, or chronic neurological deficit TIAs, h/o of stroke Brain tumors Metastatic disease Dementia Epilepsy Chronic headaches MS Developmental delay Pituitary disorders Cranial nerve dysfunction

CT Head For acute neurologic eventsCT of the head without IV contrast
The most frequent reason that a CT head is ordered is for the diagnosis of CVA’s and ICH Does not exclude infarct in acute stage of a stroke, but is useful to exclude a bleed (so anticoagulant medication can be commenced) IV contrast is not routinely used, but may be useful for evaluating tumors, cerebral infections, and sometimes for the evaluation of stroke patients.

CT Head CT can also be used to detect increases in intracranial pressure, e.g. before lumbar puncture or to evaluate the functioning of a VP shunt. CT is used in trauma for evaluating facial and skull fractures. In order to prevent unnecessary irradiation of the orbits and especially the lenses, head CTs are performed at an angle parallel to the base of the skull, with the patient in the supine position. Slice thickness generally is between 5 and 10 mm

MRI Currently, MRI with Diffusion Weighted Imaging:
MRI is also performed for possible brain stem and posterior brain pathology, that is not readily seen on CT Currently, MRI with Diffusion Weighted Imaging: Is superior to CT in detecting acute infarcts Is less sensitive than CT for SAH and hyperacute parenchymal hemorrhage Has no exposure to radiation, but takes longer to get study done

Imaging Techniques CT MRI-T1 MRI-T2 Bone Bright Dark Air Fat Water
Brain Intermed Gray=gray White=white

Imaging Techniques Normals CT vs MRI-T vs MRI-T2

Imaging Techniques CT MRI-T1 MRI-T2 Acute Bleed Bright Tumor Dark
Infarct Calcifications IV Contrast

CT Angiography (CTA) Advantages: Disadvantages: Noninvasive
Faster than MRA or Angiography Excellent for measuring lesions Easily demonstrates intraluminal clots and extravascular hematomas Disadvantages: Radiation exposure Use of contrast material Can be diagnostic, but may require invasive therapeutic measures

Magnetic Resonance Angiography (MRA)
Advantages: -Noninvasive -Iodinated Contrast not needed -Safe for patients with renal insufficiency -Images can be reconstructed in any plain -Does not require the use of radiation -Depicts both anatomy and flow rate Disadvantages: -Can not be used in patients with pacemakers or certain hardware -Long acquisition time -Poor spatial relations -Can be diagnostic but may require invasive therapeutic measures

Angiogram Advantages: Disadvantages:
Can be diagnostic and theurapeutic Although invasive, if a clot or aneurysm is seen, intervention can be done at the time of the procedure Disadvantages: Invasive Use of Contrast Material Possible Kidney failure Lengthy post-procedure precautions for bleeding from insertion site

A 82 y/o female presents with sudden onset of right-sided weakness and garbled speech for 3 hours. What, if any, radiologic test would you order, and why? Answer: CT of head without IV contrast. Why, you ask? As you can see from the above info, both IV contrast and an acute bleed will show up bright on CT. You must first rule out hemorrhage in any acute stroke patient, so that appropriate therapy can be started. You wouldn’t want to start thrombolytic therapy on someone who is actively bleeding!!!

Mini Quiz Which of the following is NOT true concerning the process of performing a head CT? A. Head CTs are performed at an angle parallel to the base of the skull. B. Slice thickness is generally between 5 and 10 mm. C. Intravenous contrast is routinely used. D. The patient is placed in a supine position on the table.

Stroke

68 y/o with left-sided weakness and confusion
CT Head w/o Contrast

Ischemic Stroke Ischemic strokes account for 84% of all strokes
Causes: Thrombosis Blood clot forms in one of the cerebral arteries from hypercoagulable state, rupture of atherosclerotic plaque, or underlying stenosis May be preceded by transient ischemic attack (TIA) Embolism Detached clot from heart or large vessels such as carotid Afib is a common cause Hypoperfusion Proximal stenosis of cerebral artery Cardiac or respiratory failure Lacunar infarctions walls of small arteries thicken and cause the occlusion of the artery involve the small perforating vessels of the brain and result in lesions that are less than 1.5 cm in size. Sharply circumscribed hypodense edema (arrowheads) in the right middle cerebral artery territory

Early CT findings in acute infarct
May be normal in first ~ 12 hours Loss of gray-white matter differentiation Loss of bright cortical ribbon Subtle hypodensity (cytotoxic edema) Loss of bright basal ganglia Swelling/sulcal effacement Hyperdense artery sign Artery must be brighter than other Circle of Willis arteries Artery in question must fit clinical picture CT showing acute infarct with loss of gray-white matter differentiation (arrows) and sulcal effacement

79 y/o female with HA and ataxia
CT Head w/o contrast

Hemorrhage in the left posterior parietal lobe (arrow)
Hemorrhagic Stroke Hemorrhagic strokes are due to rupture of a cerebral blood vessel that causes bleeding into or around the brain. 2 Types (intracerebral and subarachnoid) Intracerebral Hypertensive hemorrhage (most common cause) Predilection for deep structures of the brain, such as thalamus, pons, cerebellum, and basal ganglia Amyloid angiopathy Ruptured vascular malformation Coagulopathy Hemorrhage into a tumor Drug Abuse Hemorrhage in the left posterior parietal lobe (arrow)

28 y/o female with “worst HA of my life”
CT head w/o contrast

Subarachnoid Hemorrhage
Main causes: Trauma #1 Ruptured cerebral aneurysm Other Causes: AVM rupture Coagulopathy Vasculitis Neoplasm Pituitary apoplexy Hypertension Venous rupture/venous thrombosis NONCONTRAST CT is the imaging of choice for nontraumatic SAH If CT is negative and there is still a strong clinical suspicion→ LP may be used for the diagnosis Detection of a subarachnoid hemorrhage is crucial because the rehemorrhage rate of ruptured aneurysms is high and rehemorrhage is often fatal. On CT, a subarachnoid hemorrhage appears as high density within sulci and cisterns. High density blood fills the third ventricle and is in the sylvian fissure in this subarachnoid hemorrhage.

After positive SAH on CT or lumbar puncture:
Cerebral (catheter) angiography: “Gold standard” Invasive Time and labor intensive Small risk of complications (stroke, contrast reaction) CTA—best first exam; replaces cerebral angiography in many cases Minimally invasive (IV injection) Very fast Moderately labor intensive May still need catheter angiography if CTA is negative, or aneurysm not well delineated Iodinated contrast risk

25 y/o with new onset seizures

Arteriovenous Malformation with Hemorrhage
Underlying AVM may or may not be visible on CT scan Prominent vessels adjacent to the hematoma suggest an underlying arteriovenous malformation Some arteriovenous malformations contain dysplastic areas of calcification and may be visible as serpentine enhancing structures after contrast administration. The CT on the top shows hemorrhage (arrow) due to underlying AVM (arrowheads). The arteriogram on the left shows the tangle of vessels (arrowheads) of the AVM. This lesion would be considered for intravascular embolic therapy.

The most important issue to determine when imaging a stroke patient is whether a hemorrhagic or ischemic event has occurred. B. False A. True

Which of the following is NOT true concerning stroke?
B. An embolic stroke occurs when a detached clot flows into and blocks a cerebral artery. C. Global anoxia presents an ischemic challenge to the brain and is classified as a hypoperfusion infarction. D. The most common cause of non-traumatic intracerebral hematoma is hypertensive hemorrhage. A. Hemorrhagic stroke is more common than ischemic stroke.

In which of the following locations is hypertensive hemorrhage LEAST LIKELY to occur? A. Thalamus B. Cerebellum C. Basal Ganglia D. Pons E. Occipital Lobe

Which of the following is NOT true concerning CT of a stroke patient? A. Patients who have a hypertensive hemorrhage may have extension of blood into the ventricular system. B. An acute infarct may be normal on CT for the first 12 hours. D. On CT, prominent vessels adjacent to a hematoma suggest an underlying arteriovenous malformation. C. The underlying arteriovenous malformation causing stroke is almost always visible on CT scan.

Which of the following is NOT a CT finding in an acute infarct. A
Which of the following is NOT a CT finding in an acute infarct? A. Loss of gray-white distinction B. Subtle hypodensity due to cytotoxic edema C. Hyperdensedense basilar or middle cerebral artery corresponding to thrombus in the affected vessel. E. Sulcal effacement D. Dysplastic areas of calcification

Which of the following is NOT true concerning subarachnoid hemorrhage
Which of the following is NOT true concerning subarachnoid hemorrhage? A. Appears as high density within sulci and cisterns. B. Noncontrast CT is the imaging of choice for suspected SAH. D. Cerebral angiography is the “gold standard.” E. Subarachnoid hemorrhage occurs most commonly with trauma C. The rehemorrhage rate of a SAH is low.

Trauma

17 y/o status-post MVA CT head w/o contrast

Linear skull fracture of the right parietal bone (arrows).
The bone windows must be examined carefully. A skull fracture is most clinically significant if the paranasal sinus or skull base is involved. Raccoon Eyes Battle’s Sign Skull fractures are categorized as linear or depressed Linear fractures are more common, resembling a thin line w/o distortion or depression of bone Depressed fractures are breaks in bone with depression of bone in towards brain Fractures must be distinguished from sutures that occur in anatomical locations (sagittal, coronal, lambdoidal) and venous channels. Sutures have undulating margins Both sutures and venous channels have sclerotic margins. Venous channels have undulating sides Linear skull fracture of the right parietal bone (arrows).

55 y/o male fell from roof CT head w/o contrast

Traumatic Intraventricular Hemorrhage
Traumatic intraventricular hemorrhage is associated with diffuse axonal injury, deep gray matter injury, and brainstem contusion. An isolated intraventricular hemorrhage may be due to rupture of subependymal veins. As you can see, this patient also has a SAH, which, if you remember, is most commonly caused by TRAUMA! -The ruptured vessel bleeds into the space between the pia and arachnoid matter. -The most common location of posttraumatic subarachnoid hemorrhage is over the cerebral convexity. -This may be the only indication of cerebral injury. Intraventricular hemorrhage (arrow) found in a trauma patient. Note the subarachnoid hemorrhage in the sulci in the subarachnoid space (arrowheads).

47 y/o alcoholic “found down”

Subdural Hematoma Deceleration and acceleration or rotational forces that tear bridging veins can cause an acute subdural hematoma. The blood collects in the space between the arachnoid matter and the dura matter. Subacute Compressed lateral ventricle Effaced sulci White matter “buckling” Thick cortical “mantle” Acute Crescent shaped, concave toward brain Tapering edges Crosses suture lines May extend into interhemispheric fissure Fracture may or may not be present Hyperdense, may contain hypodense foci due to serum, CSF or active bleeding High density, crescent shaped hematoma overlying the left cerebral hemisphere. Note the shift of the normally midline septum pellucidum due to the mass effect

19 y/o post fist fight-5 hours later has acute LOC

Epidural Hematoma An epidural hematoma is usually associated with a skull fracture. The fractured bone lacerates a dural artery or a venous sinus. Most common artery involved is the middle meningeal artery The blood from the ruptured vessel collects between the skull and dura. Hyperdense, lens shaped (lenticellular) biconvex mass Abrupt edges Does not cross sutures Cannot extend into interhemispheric fissure Biconvex mixed hyperdense and hypodense lesion overlying the left frontal cortex. Notice that it does not cross suture lines.

47 y/o status-post car vs. tree

Diffuse Axonal Injury Diffuse axonal injury is often referred to as "shear injury“, caused by acceleration, deceleration, and rotational forces Portions of the brain with different densities move relative to each other resulting in the deformation and tearing of axons. Immediate loss of consciousness is typical of these injuries. The CT of a patient with diffuse axonal injury may be normal despite the patient's presentation with a profound neurological deficit. May appear as ill-defined areas of high density or hemorrhage in characteristic locations, listed from most likely location first followed by successively less likely locations: - Subcortical white matter - Posterior limb internal capsule - Corpus callosum - Dorsolateral midbrain Hemorrhage of the posterior limb of the internal capsule (arrow) and hemorrhage of the thalamus (arrowhead).

92 y/o restrained driver in MVA

Cerebral Contusions Cerebral contusions are the most common primary intra-axial injury, caused by coup/contrecoup injury They often occur when the brain impacts an osseous ridge or a dural fold. Multiple petechial hemorrhage or edema are located along gyral crests. The following are common locations: - Temporal lobe - anterior tip, inferior surface, sylvian region - Frontal lobe - anterior pole, inferior surface - Dorsolateral midbrain - Inferior cerebellum On CT, cerebral contusion appears as an ill-defined hypodense area mixed with foci of hemorrhage. After hours, hemorrhagic transformation or coalescence of petechial hemorrhages into a rounded hematoma is common. Multiple foci of high density corresponding to hemorrhage (arrows) in an area of low density (arrowheads) in the left frontal lobe due to cerebral contusions.

Which of the following is NOT true concerning acute subdural hematoma
Which of the following is NOT true concerning acute subdural hematoma? A. Tearing of bridging veins causes acute subdural hematoma. C. The hematoma is crescent shaped on CT. D. The hematoma may extend into hemispheric fissure B. The hematoma is lenticellular in shape on CT.

The most common cause of subarachnoid hemorrhage is trauma.
B. False A. True

Which of the following is NOT a characteristic of subacute subdural hematoma? A. Compression of the lateral ventricle on the side of the hematoma. B. Effaced sulci. C. White matter buckling. D. Thick cortical mantle. E. Insular ribbon sign.

Which of the following is NOT true regarding a epidural hematoma?
A. Caused by laceration of dural artery or venous sinus C. Blood collects between the skull and the dura D. Blood does not cross suture lines B. Not usually associated with a skull fracture.

Which of the following is NOT true concerning subacute subdural hematoma?
B. It should be suspected when there is a midline shift of structures without an obvious mass present. C. On CT, the hemorrhage is hyperdense to normal gray matter. D. Blood collects in the space between the arachnoid matter and the dura matter. A. Contrast is often used to visualize the hematoma on CT.

65 y/o WM with mental status changes and left sided weakness
CT head w/o contrast CT head with contrast

Glioblastoma Multiforme
Glioblastoma Multiforme is the most aggressive grade of astrocytoma. On CT, GBM is characterized by necrosis and irregular enhancement. It is one of very few lesions that frequently cross the corpus callosum. Differentiating Intra-axial tumors: Tumor completely surrounded by brain Effaced CSF spaces Gray–white junction not displaced inward Cortical vessels not displaced inward Bone normal (rare: remodeling of inner table in cortical tumors) An image post contrast administration in the same patient reveals patchy enhancement, a portion of which is crossing the corpus callosum (arrow).

23 y/o with new onset seizures
T1 MRI T2 MRI

Meningioma Meningiomas are the most common extra-axial neoplasm of the brain. Twenty percent of meningiomas calcify. On CT, meningiomas are usually isointense to gray matter. Differentiating Extra-axial tumors Tumor borders on CSF space Enlarged CSF spaces at edges of mass Gray–white junction displaced inward Cortical vessels displaced inward Bone may have hyperostosis (meningioma) or remodeling On this T2 weighted MRI this meningioma is extra-axial and compressing adjacent brain structures, displacing the gray-white junction inward. Notice the “crinkling” of the displaced brain.

53 y/o male with hx of melanoma, with headache and gait disturbance
CT head w/o contrast CT head with contrast

Metastatic Tumors Metastatic tumors are the most common intracranial tumors in adults. Most common sites are from lung, breasts, melanoma, renal, and colon. Mets commonly occur at the corticomedullary junction, and the edema pattern is usually larger than the tumor Unenhanced and enhanced CT show multiple high attenuation lesions without contrast, with enhancement after contrast, as well as surrounding edema

True or False 1. Lymphomas are the most common extra-axial neoplasm of the brain. A. True 2. On CT, meningiomas are usually isointense to gray matter. B. False 3. MRI is more sensitive than CT for meningioma. B. False 4. Like most tumors, glioblastoma multiforme does not cross the corpus callosum. A. True 5. On CT, glioblastoma multiforme is characterized by necrosis and irregular enhancement. B. False B. False A. True A. True B. False A. True

Degenerative

74 y/o male with chronic memory loss and impaired executive function

Alzheimer’s Because of its low sensitivity and specificity for the diagnosis of Alzheimer's disease, imaging is typically not used to rule in Alzheimer's disease but rather to rule out other causes of dementia. Nevertheless, in the right clinical context Alzheimer's disease appears radiographically as diffuse cerebral atrophy with enlarged lateral ventricles and widened sulci on CT. Large cortical neurons in the transentorhinal region are the major types of neurons that undergo this degeneration. This process begins focally in the fronto/temporal lobes (primarily the entorhinal cortex and hippocampal regions) succeeded by the parietal lobes and finally the occipital lobes. The neuronal loss is severe resulting in marked, diffuse atrophy that may be as much as 10-30% of the total brain mass In this CT, you can see enlarged ventricles with atrophy of the cerebral hemispheres without any other visible causes of the dementia

95 y/o with dementia CT head w/o contrast

Cerebral Atrophy Cerebral atrophy refers to the wasting away of brain tissue and cells that occurs as part of normal aging It is important to distinguish if atrohy is “normal for patient age” See widening of sulci and narrowing of the gyri Cerebral atrophy can also be secondary to Stroke Alzheimer’s Pick’s Disease Infectious Huntington’s Cerebral palsy Drugs HIV CT shows diffuse atrophy with widened Sylvian cisterns

65 y/o male with resting tremor and masked facies
T2-MRI

Parkinson’s Disease A clinical syndrome, Parkinson's disease is clinically evident by its triad of bradykinesia and hypokinesia, resting tremor, and increased tonicity of voluntary musculature and loss of postural reflexes. There is a selective loss of neuromelanin containing dopaminergic neurons within the pars compacta of the substantia nigra, and the disease manifests itself when 80% of these neurons are lost. Radiographically Parkinson’s disease appears as nonspecific atrophy with enlarged lateral ventricles and widened sulci on CT. On MR, decreased width of the pars compacta between the pars reticularis and the red nucleus may be evident. There is no cure for Parkinson's disease. The arrows indicate areas of decreased width of the low signal intensity pars compacta within the substantia nigra.

52 y/o male with spastic flailing of extremities

Huntington’s Disease Huntington’s disease is a progressive neurodegenerative disorder characterized by choreoathetoid movements, behavioral disturbances, and progressive dementia. Huntington's disease is a known genetically linked disorder with autosomal dominant inheritance and complete penetrance. Huntington's disease is caused by a trinucleotide repeat that is found within the huntingtin gene located on chromosome 4. Grossly changes are initially manifested by striatal atrophy Degeneration occurs most prominently in the caudate tail followed by the body, head, and eventually the putamen and nucleus accumbens. By the time the disease reaches its terminal phases, 20-30% of the total brain mass may be reduced. There is no cure for Huntington's disease, and it is universally fatal. The image on the left exhibits bilateral caudate head atrophy (red arrowheads), as seen by a decrease in the medial convexities, & lateral ventricle dilatation. Generalized atrophy evident as diffusely widened sulci is also apparent in the image on the left

72 y/o male preacher with seductive behaviors, cussing, and dementia

Pick’s Disease Pick’s Disease is a neurodegenerative disorder that is clinically evident as behavioral and language disturbances out of proportion to memory deficits. Following Alzheimer’s disease and diffuse Lewy body disease, Pick’s disease is the third most common neurodegenerative cortical dementia. Due to severe neuronal loss and gliosis, atrophy becomes readily apparent in those regions of the cortex most commonly affected, the frontal and temporal lobes. This atrophy may be asymmetric. Currently there is no treatment. Focal bifrontotemporal atrophy can be seen, as exhibited by marked widening of the frontal and temporal sulci, dilation of the lateral ventricles, and the "knife-like" projections of the gyri.

Imaging is typically used to rule in the diagnosis of Alzheimer's disease.
A. True B. False

Huntington's disease is characterized by the selective degeneration of neurons within the striatum.
B. False A. True

The process responsible for Alzheimer's disease begins focally in the _______________.
A. parietal lobes B. occipital lobes D. brainstem C. fronto/temporal lobes

On axial T2-weighted MRI, decreased width of the pars compacta may be evident in patients with Parkinson's disease. B. False A. True

On CT, Huntington's disease appears as _________________________________.
B. Decrease in the relative volume of the lateral ventricles. C. Both A and B. D. Neither A nor B. A. Decrease in the convexity of the caudate heads bilaterally.

On CT in Pick's disease, one might observe which of the following?
A. widening of the Sylvian fissure B. atrophy of the inferior frontal and superior temporal lobes C. sulcal prominence D. enlargement of the frontal horns of the lateral ventricles E. all of the above

Infections

5 month old with HA, neck stiffness, and photophobia

Diffuse leptomeningeal enhancement can be seen overlying the cortex
Meningitis Three subtypes of meningitis. Acute pyogenic meningitis is usually bacterial. Lymphocytic meningitis is usually viral, benign and self-limited. Chronic meningitis is often seen in immunocompromised hosts and may be fungal or parasitic. Imaging usually on done to look for complications and assess for safety of LP Imaging is usually normal, so it is not usually performed for diagnosis Diffuse leptomeningeal enhancement can be seen overlying the cortex

Meningitis Common complications of meningitis that can be seen using imaging techniques: Hydrocephalus Ventriculitis/ Ependymitis Subdural effusion Subdural empyema Cerebritis/ Abscess Vasospasm The development of cerebrovascular problems is the most common complication of meningitis. Arterial infarction can occur which often affects the basal ganglia due to the occlusion of small perforating vessels. Hemispheric infarction can also occur due to major vessel spasm. Venous infarctions are also common and can include cortical venous occlusion or the involvement of the superior sagittal sinus.

23 y/o male with acute mental status change
CT head w/o contrast DWI-MR

Herpes Encephalitis MRI with DWI highly sensitive
CT may be negative or misinterpreted as infarct/tumor early in course Anterior temporal lobes, basal frontal lobes, cingulate cortex, insular cortex (limbic system) Spares basal ganglia Bilateral ~ 50% Hemorrhage or enhancement not until subacute or chronic phase As you can see, CT appears normal, but on DWI MR, the right temporal lobe lights up (arrow)

19 y/o male with hx of meningitis with continued fever and confusion
CT head with contrast

Ventriculitis/Ependymitis
Ventriculitis is characterized by inflammation and enlargement of the ventricles. Ependymitis shows hydrocephalus with damage to the ependymal lining and proliferation of subependymal glia. A CT of patients with these conditions reveals the presence of periventricular edema and subependymal enhancement. Ventriculitis and Ependymitis affect approximately 30% of the adult patients and 90% of the pediatric patients with meningitis. In this post contrast CT scan, note the ring enhancing brain abscess (arrowheads) and enhancement of the ependymal lining of the atrium by the left lateral ventricle (arrow)

35 y/o female with HA and fever
T1-MRI with Gad

Notice the mass ring enhancing mass (arrows) with surrounding edema
Brain Abscess Ring enhancing mass(es) with edema Location: anywhere, often gray-white junction Wall of abscess uniform width; may be thinner at deep margin Ddx: Necrotic glioma, metastases (irregularly thick, nodular walls) CT & MR with contrast both highly sensitive DWI: very bright in abscess Ddx: necrotic tumor MR spectroscopy accurate for abscess vs. necrotic tumor Notice the mass ring enhancing mass (arrows) with surrounding edema

35 y/o AIDS patient with fever, HA, and seizures

Multiple ring enhancing lesions seen at many levels (arrows)
Toxoplasmosis Caused by a single celled parasite called Toxoplasma gondii Typically seen in immunocompromised or infants born to mothers with an active infection during pregnancy May infect the brain, lung, heart, eyes, or liver May appear as multiple ring enhancing lesions MRI is considered the best imaging technique for toxoplasmic encephalitis Multiple ring enhancing lesions seen at many levels (arrows)

Ring-enhancing brain lesions
Lots of things can show up as ring-enhancing lesions, so even though it sounded really cool in medical school, it is really not very specific! “MAGICAL DR” Metastasis Abscess Glioblastoma/high grade glial neoplasm Infarct (subacute; esp. in deep gray nuclei) Contusion (subacute) AIDS (Toxo) Lymphoma (in immunocompromised) Demyelinating lesion Resolving hematoma (subacute)

Imaging studies of patients with meningitis are frequently normal despite the presence of the disease. B. False A. True

Typical findings on CT of patients with ventriculitis or ependymitis are periventricular edema and subependymal enhancement. B. False A. True

Which of the following is NOT true concerning cerebrovascular complications of meningitis? A. The development of cerebrovascular problems is the most common complication of meningitis. B. Arterial infarction can occur and often affects the basal ganglia. C. Major vessel spasm can occur causing hemispheric infarction. D. Complications of meningitis can include cortical venous occlusion. E. Venous infarctions resulting from meningitis do not involve the superior sagittal sinus.

A ring enhancing lesion is diagnostic of toxoplasmosis
A. True B. False

67 y/o male with gait disturbance, dementia, and urinary incontinence

Hydrocephalus Abnormal buildup of CSF in the brain Two types
Communicating Inadequate reabsorption of CSF Nonobstructing Noncommunicating Blockage of CSF Can be associated with Tumors Trauma Meningitis Arachnoid cysts Congenital SAH Normal pressure hydrocephalus CT shows enlargement of bilateral lateral ventricles with shrinking of adjacent brain matter

38 y/o female with numbness in LUE
T2 MRI T2 MRI

Multiple Sclerosis MRI: imaging study of choice
MS is due to myelin loss in multiple areas leading to sclerosis Small, discrete white matter lesions: Periventricular (esp. perpendicular to ventricle) Peripheral brainstem Undersurface of corpus callosum Subcortical white matter Variable enhancement; usually no edema T2 weighted MRI showing “plaques” (arrows) in both the brain and the spinal cord

Final Quiz (cross your fingers, because you’re almost done!)

B. The hematoma may cross suture lines.
Question 1: Which of the following is NOT true concerning epidural hematoma? A. Epidural hematoma is caused by the laceration of a dural artery or venous sinus by a fracture. C. On CT, the hematoma forms a hyperdense, biconvex mass. D. On CT, the hematoma may contain hyperdense foci due to active bleeding. E. The hematoma may cross dural reflections. B. The hematoma may cross suture lines. Explanation: An epidural hematoma occurs when an artery ruptures and blood collects between the dura and the skull. At suture lines, the dura tightly adheres to the calvarium. Since an epidural hematoma does not cross these tight junctions occur, it is not seen crossing suture lines.

Question 2: Which of the following is NOT true concerning cerebral contusion? A. Cerebral contusion often occurs when the brain impacts an osseous ridge or dural fold. B. On CT, cerebral contusions appear as ill-defined hypodense areas. C. On CT, cerebral contusions are often mixed with foci of hemorrhage. D. After 1 to 2 days, coalescence of petechial hemorrhages into a rounded hematoma is common. E. The occipital, temporal, and parietal lobes are the most common locations of cerebral contusion. Explanation: Cerebral contusions most commonly occur in the anterior tip, the inferior surface and sylvian region of the temporal lobe, the anterior pole and inferior surface of the frontal lobe, the dorsolateral midbrain, and the inferior cerebellum.

Question 3: Which of the following is NOT true concerning diffuse axonal injury?
A. Diffuse axonal injury can present with a normal head CT. B. Diffuse axonal injury is the most common cause of morbidity in CNS trauma. C. Diffuse axonal injury is often associated with intraventricular hemorrhage. E. Acceleration, deceleration, and rotational forces cause diffuse axonal injury. D. On CT, diffuse axonal injury appears as ill-defined areas of high density or hemorrhage. Explanation: On CT, diffuse axonal injury occurs as ill-defined areas of low density. The often accompanying hemorrhage appears as bright spots of high density.

B. Subarachnoid hemorrhage over cerebral convexities.
Question 4: Given the following CT, the most likely diagnosis is: A. Diffuse axonal injury. C. Subdural hematoma. D. Hypertensive hemorrhage in the occipital lobe. B. Subarachnoid hemorrhage over cerebral convexities. Explanation: The arrows in the image indicate the areas of high density that correspond to hemorrhage over cerebral convexities.

C. Glioblastoma multiforme
Question 5: The CT on the top, taken prior to contrast administration and the CT on the bottom, taken after contrast administration, show: A. Epidural hematoma. B. Subarachnoid hemorrhage. D. Subdural empyema. C. Glioblastoma multiforme Explanation: The gliobastoma in the right frontal lobe is outlined by arrows in the images here. Notice the enhancement of the edges of the tumor upon contrast administration (bottom), and how the tumor crosses into the left hemisphere.

Question 6: Given the following head CT, the most likely diagnosis is:
B. Epidural hematoma. C. Chronic subdural hematoma. D. Subarachnoid hemorrhage. A. Acute subdural hematoma. Explanation: The arrowheads outline the high-density, crescent-shaped hematoma overlying the right cerebral hemisphere. Note the hypodense region (red arrow) within the high-density hematoma (blue arrows), which may indicate active bleeding. The high density and active bleeding are indicative of an acute subdural hematoma.

C. Diffuse axonal injury.
Question 7: Given the following head CT, the most likely diagnosis is: A. Hypertensive hemorrhage in the frontal lobe. B. Subarachnoid hemorrhage over cerebral convexities. D. Intracranial tumors. C. Diffuse axonal injury. Explanation: The arrows indicate the hemorrhage in the subcortical white matter of the left frontal lobe. Such hemorrhage often accompanies diffuse axonal injury, the direct evidence of which (ill-defined areas of low density) is not always apparent on CT. (see question 3)

D. Diffuse axonal injury
Question 8: Which of the following is NOT shown in this CT? A. Intraventricular hemorrhage B. Subarachnoid hemorrhage C. Diffuse hypodensity D. Diffuse axonal injury Explanation: The intraventricular hemorrhage is clearly visible as the high density blood in the left lateral ventricle. The area of high density in the left cerebral hemisphere is the location of the subarachnoid hemorrhage (red arrow). Areas of low density around the subarachnoid hemorrhage are diffuse hypodensity as a result of edema (blue arrow).

A. CT can be rapidly performed.
Question 9: Which of the following is NOT an advantage to performing a CT scan for stroke? A. CT can be rapidly performed. C. CT allows easy exclusion of hemorrhage. D. CT allows the assessment of parenchymal damage. B. It is always possible to distinguish between old and new infarcts. Explanation: It is not always easy to distinguish between old and new infarcts. MR is a better in this regard. Other disadvantages of CT are its current lack of functional information and limited ability to evaluate the vertebrobasilar system.

Question 10: Which of the following is NOT true concerning CT?
A. CT is the imaging modality of choice for the detectiing of subarachnoid hemorrhage. B. Small subarachnoid bleeds may be inapparent. C. On CT, subarachnoid hemorrhage appears as high density within sulci and CSF cisterns. D. CT becomes more sensitive days to weeks after the acute phase of a subarachnoid hemorrhage. Explanation: Blood is reabsorbed from CSF days to weeks after the acute phase of a subarachnoid hemorrhage. As this occurs, the hemorrhage becomes isodense to the brain. Thus, CT becomes less sensitive in detecting subarchnoid hemorrhage.

Neuroradiology for Medical Students

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