Imaging of Traumatic Brain Injury: Pearls and Pitfalls

This was presented at the 51st Annual Scientific Meeting of the Royal College of Radiologists of Thailand.

Slideshow: Imaging of Non-traumatic Intracranial Hemorrhages

Imaging of Non-traumatic Intracranial Hemorrhage from Rathachai Kaewlai

Tuberous Sclerosis Complex

Axial T1W MR image of a 5-year-old girl demonstrates several T1-hyperintense subependymal nodules arrows).

Coronal FLAIR MR image shows multiple cortical tubers and subcortical white matter hyperintensities (asterisks).

Facts

• Autosomal dominant disorder due to abnormality of TSC1 and TSC2 genes
• Most frequent clinical manifestations are neurologic (myoclonic seizures in early childhood, psychiatric symptoms, retinal hamartomas) and skin (adenomas of sebaceous glands)

Diagnostic Criteria by Tuberous Sclerosis Complex Consensus Conference (Maryland 1998)

Major features

• Facial angiofibromas or forehead plaque
• Nontraumatic ungual or periungual fibroma
• Hypomelanotic macules (more than 3)
• Shagreen patch (connective tissue nevus)
• Cortical tuber
• Subependymal nodule
• Subependymal giant cell astrocytoma
• Multiple retinal nodular hamartomas
• Cardiac rhabdomyoma, single or multiple
• Lymphangiomyomatosis (LAM)
• Renal angiomyolipoma (AML)

Minor features

• Multiple randomly distributed pits in dental enamel
• Hamartomatous rectal polyps
• Bone cysts
• Cerebral white matter "migration tracts"
• Gingival fibromas
• Nonrenal hamartoma
• Retinal achromic patch
• Confetti skin lesions
• Multiple renal cysts

Definite TSC: Either 2 major, or 1 major + 2 minor features

Probable TSC: One major + one minor feature

Possible TSC: Either 1 major, or 2 or more minor features

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Imaging findings are highlighted in red.

When both LAM and renal AML are present, other features should be present as well before definite diagnosis is made. 

Reference:

Roach ES, Sparagana SP. Diagnosis of tuberous sclerosis complex. J Child Neurol 2004;19:643-649. Fulltext

Sellar Mass with Calcification

Sagittal images (upper left = CT, upper right = T2W MR, lower left = T1W MR, lower right = T1W post-contrast MR) of the pituitary region of an elderly individual show a large sellar/suprasellar mass with internal calcification (hyperdense on CT, signal loss on MR). The mass is mostly solid and reveals heterogeneous enhancement. Note ballooning of the sella.

Differential diagnosis of a calcified sellar mass:

• Craniopharyngioma (most likely)
• Pituitary adenoma (unlikely, 0.2% - 8% have calcification)
• Rathke's cleft cyst (rare disease)
• Chordoma (rare disease)

Associated findings that help DDx:

• Nodular appearance of calcification --> craniopharyngioma
• Calcifications in a cystic mass --> craniopharyngioma
• Curvilinear appearance of calcification --> pituitary adenoma or Rathke's cleft cyst
• Bone destruction --> chordoma

This is a rare case of sellar/suprasellar chondrosarcoma confirmed with histology. 

Reference:

Kasliwal MK, Sharma BS. A rare case of pituitary adenoma with calcification: a case report. Turkish Neurosurg 2008;18:232-235

Glezer A, et al. Rare sellar lesions. Endocrinol Metab Clin N Am 2008;37:195-211. 

Olfactory Groove Meningioma

Axial T2W MR image shows a lobulated extraaxial mass in the midline anterior cranial fossa. The mass is T2 isointense with a central area of higher T2 signal intensity. Mild brain edema of the inferior frontal lobes are noted. 

Sagittal post-contrast T1W MR image shows uniform enhancement of the mass.  It better demonstrates the location of the mass that is anterior to the tuberculum sellae.

Facts: Olfactory Groove Meningioma

• Usually asymptomatic until large. 
• When symptomatic, they can produce Foster Kennedy syndrome (anosmia, ipsilateral optic atrophy, contralateral papilledema), metal status change, urinary incontinence
• Histological variables follow WHO grading I to III (from low recurrence to high rates of recurrence with aggressive growth)
• Atypical meningioma, rhabdoid and malignant meningioma have greater risk of recurrence
• Brain invasion increases likelihood of recurrence but not indicator of malignant grade
• "Olfactory groove" is anterior to tuberculum sellae (distinction between tuberculum vs olfactory groove meningioma). Tuberculum sellae is bony elevation between chiasmatic sulcus and sella turcica. See tuberculum sellae meningioma here (external site)

MRI Findings

• T1 and T2 isointensity
• Most enhances with gadolinium
• Dural tail
• Signal voids in the lesion due to calcifications

Reference:

Cranial Base Center of Massachusetts General Hospital website 

Slideshow: Imaging of Traumatic Brain Injury

Imaging of Traumatic Brain Injury from Rathachai Kaewlai

Arachnoid Cyst

Axial T1W MR image shows a large T1 hypointense extra axial lesion in the left parietal region (arrow). 

Coronal T2GRE and T2W images demonstrate homogeneous T2 hyperintensity of the mass that follows CSF signal. There is compression of the adjacent gyri.  

Facts: Arachnoid Cyst

• Congenital lesion arising during development from splitting of arachnoid membrane
• Contains fluid usually identical to CSF
• Do not communicate with ventricles or subarachnoid space
• Lined with meningothelial cells 
• Incidence: 5 in 1,000 autopsies. 1% of intracranial masses
• Predominant male
• Mostly asymptomatic

Imaging:

• Extraaxial cystic mass with pressure effect to underlying brain
• Signal intensity follows CSF in all sequences
• No restricted diffusion
• Most common location (from highest to lowest frequency: Sylvian fissure (almost 50%), cerebellopontine angle, supracollicular, vermin, sella/suprasella

Reference:

Greenberg MS. Handbook of Neurosurgery, 7th edition. 2010

Early Signs of Ischemic Brain Injury on Noncontrast CT

Axial noncontrast CT images of the brain of two different patients presenting with acute stroke within 3 hours of symptom onset. The top row is images in a "brain" window, while the bottom row shows images in an "acute stroke" window. Early ischemic changes (cortical ribbon sign) of the right posterior inferior cerebral artery (left images) and right middle cerebral artery (right images) are much better appreciated on the acute stroke window.  

Loss of gray-white differentiation

• Lenticular obscuration: loss of distinction among basal ganglia nuclei
• Insular ribbon sign: blending of densities of cortex and white matter of insula
• Cortical ribbon sign:  blending of densities of cortex and white matter of other lobes

Swelling of gyri producing sulcal effacement

Detectability

• Seen on less than 1/3 of patients imaged within 3 hours of symptom onset
• Detection influenced by infarct size, severity and time between symptom onset and imaging
• Large interobserver variability, which may be improved by the use of a structured scoring system such as Alberta Stroke Program Early CT Score (ASPECTS) or the CT Summit Criteria, as well as the use of better CT windowing and leveling (use of "acute stroke" window)

Implications of these signs to management

• More rapid these signs become evident, the more profound the degree of ischemia
• Presence, clarity and extent of these signs on noncontrast CT correlates with higher risk of hemorrhagic transformation after Rx with fibrinolytic agents
• Involvement of greater than 1/3 of MCA territory increases risk of intracranial hemorrhage, shown in a European trial in patients of less than 6-hour symptom onset. This criterion has been used as an exclusion from entry in several trials evaluating the benefit of IV fibrinolytic therapy in the 3- to 4.5-hour window

Reference:
Jauch EC, et al. Guidelines for the early management of patients with acute ischemic stroke: a guideline for healthcare professionals from the American Heart Association/American Stroke Association. Stroke 2013 (January)

Acute Isodense Subdural Hematoma

Plain and contrast-enhanced axial CT images of the brain show an isodense subdural hematoma (SDH, arrows) in the left cerebral convexity, much better appreciated on post-contrast image. There is also a thinner right frontal convexity SDH. 

Facts: Isodense Subdural Hematoma (SDH)

• Subdural blood collection that has similar attenuation with the gray matter
• Acute SDH appears as a high density collection with declining density with time. It passes "isodense" state mostly in subacute phase (2-6 weeks after initial trauma)
• Isodense SDH poses diagnostic dilemma because it is not apparently seen on CT
• In acute setting this can be seen in anemic patients (acute isodense SDH). Experimental data showed that Hb 8-10 g/dl will be isodense to the adjacent brain

Reference:

Smith, Jr., WP, Batnitzky S, Rengachary SS. Acute isodense subdural hematomas: a problem in anemic patients. AJR 1981; 136:543-546. 

Age-related White Matter Changes

MR FLAIR images show multiple FLAIR hyperintense foci in bilateral periventricular and deep white matter in a 77-year-old patient.

Facts:

• Several possible mechanisms but at present it is believed to be an incomplete ischemia mainly related to cerebral small vessel arteriolosclerosis
• Pathology: partial loss of myelin, axons, oligodendroglial cells; mild reactive gliosis, astrocytic gliosis, stenosis of arterioles from hyaline fibrosis
• Important substrates for cognitive impairment and functional loss in the elderly
• Very common in elderly with hypertension, diabetes, hyperlipidemai

Imaging

• Ill-defined hypodensities on CT
• T1 hypointensities, T2/PD/FLAIR hyperintensities. FLAIR best to demonstrate severity of disease
• When the largest lesion is adjacent to ventricles, it's called periventricular white matter changes
• On diffusion tensor MRI, there is elevation of diffusivity and reduced fractional anisotrophy (FA) meaning impaired white matter integrity

Reference:
Xiong YY, Mok V. Age-related white matter changes. J Aging Res 2011

Cerebral Venous Sinus Thrombosis (CVST)

Figure 1: Axial image of the brain shows ill-defined areas of hypoattenuation (stars) in bilateral frontal lobes involving both gray and white matter, in a nonarterial distribution.

Figure 2: A lateral view of CT venography shows occluded anterior 1/3 of the superior sagittal sinus (arrows).

Facts

• 0.5% of all strokes
• Peak incidence in neonates and adults in third decade of life (female:male = 5:1.5)
• Clinical presentation varies widely from relatively mild symptoms to devastating hemorrhage
• Risk factors following Virchow's triad: blood stasis, changes in vessel wall, and changes in blood composition
• Intravenous heparin and subcutaneous low-molecular-weight heparin are primary Rx for acute CVST. Hemorrhage does not preclude the diagnosis.
• Patient prognosis depends on location of CVST (best if in cortical vein, anterior superior sagittal sinus, isolated transverse and isolated sigmoid sinus) and extent of involvement (the more segments of veins involved, the greater complications)

Imaging

• Infarction or hemorrhagic infarction in non-arterial distribution
• Delta sign = filling defect (clot) surrounded by enhanced venous blood in the affected sinus and dural enhancement
• MRI shows T1 hyperintensity and lack of flow void
• Look for potential etiology (and vice versa): paranasal sinus and mastoid infection

References

1. Qureshi AI. Textbook of interventional neurology. 2011

2. Castillo M. Neuroradiology companion: methods, guidelines and imaging fundamentals. 2006

3. Zubkov AY, McBane RD, Brown D, Rabinstein AA. Brain lesions in cerebral venous sinus thrombosis. Stroke 2009;40:1509

Anaplastic Astrocytoma

Axial T2W (fig. 1) and T1W post contrast (fig. 2) images of the brain demonstrate a large ill-defined mass (arrows) centered in the right insula with extension to the frontal and temporal lobes. The mass shows a heterogeneous high T2 signal intensity, cystic areas (arrowheads), mass effect and minimal enhancement.

Facts: WHO grading system for primary astrocytic tumor and imaging features

• Grade I = circumscribed glioma including pilocytic astrocytoma -- no mass effect, no enhancement
• Grade II = diffuse astrocytoma (cytological atypia alone) -- mass effect, no enhancement
• Grade III = anaplastic astrocytoma (anaplasia and mitotic activity) -- complex enhancement
• Grade IV = glioblastoma (also show microvascular proliferation) -- necrosis (ring enhancement)

Imaging

• Imaging grading is imprecise but can be used as a preliminary assessment
• Grading is not applicable to pediatric patients or special astrocytomas
• Low grade gliomas usually hypodense on CT, hypointense on T1WI and hyperintense on T2WI. High T2 signal intensity commonly extends beyond the tumor volume. Most do not enhance.
• Anaplastic gliomas may or may not enhance. Calcifications and cysts occur in 10-20%.
• Glioblastomas usually enhance on the rim, representing cellular tumor but tumor cells often extend beyond 1.5 cm of the enhanced ring. Nonenhancing center may represent necrosis or associated cyst.
• On imaging, factors affecting prognosis are location (eloquent vs. non-eloquent) and tumor size

Our case: anaplastic astrocytoma.

Reference:

Greenburg MS. Handbook of neurosurgery, 7th edition, 2010.

2010 McDonald MRI Criteria for Diagnosis of Multiple Sclerosis

Diagnosis of Multiple Sclerosis (MS)

• Clinical + paraclinical lab assessment
• Need to demonstrate dissemination of lesions in space (DIS) and time (DIT), and exclude other diagnoses
• Since the last McDonald Criteria (2005-version), new data and consensus have agreed upon simplification of the criteria to improve comprehension and utility
• McDonald Criteria should only be applied in patients presenting with a typical clinically isolated syndrome suggestive of MS, or symptoms consistent with a CNS inflammatory demyelinating disease
• Clinical isolated syndrome typically involve the optic nerve, brainstem/cerebellum, spinal cord or cerebral hemispheres; can be monofocal or multifocal

MR Imaging Criteria for DIS / DIT

• At least one T2 lesion in at least 2 of 4 locations considered characteristic for MS (juxtacortical, periventricular, infratentorial, and spinal cord)
• A new T2 and/or gadolinium-enhancing lesion(s) on follow-up MRI, with reference to a baseline scan, irrespective of the timing of the baseline MRI
• Simultaneous presence of asymptomaatic gadolinium-enhancing and nonenhancing lesions at any time

Read full article here.

Reference:

Polman CH, Reingold SC, Banwell B, et al. Diagnostic criteria for multiple sclerosis: 2010 revisions to the McDonald Criteria. Ann Neurol 2011;69 (first published online 8 Mar 2011)

Hyperdense Middle Cerebral Artery Sign

Axial CT image (narrow window) shows a hyperdense left MCA, representing an intraluminal thrombus.

Hyperdense MCA Sign

• Visualization of high density middle cerebral artery due to presence of intraluminal thrombus
• Specific sign for thrombotic MCA occlusion, but it is not sensitive
• Associated with poor prognosis and higher risk of hemorrhage if thrombolyzed
• Early resolution indicates successful reperfusion and favorable outcome after thrombolysis

Imaging Differentials

• Intraluminal thrombus
• High hematocrit (usually bilateral)
• Calcified plaque (usually bilateral)

Reference:

Rabinstein AA, Resnick SJ. Practical Imaging in Stroke: a Case-based Approach, 2009.

Swirl Sign

An axial CT image of the brain in a trauma patient shows a hyperdense epidural hematoma (arrowheads) with a small rounded area of low attenuation (arrow) internally.

Facts: The Swirl Sign

• An area of low attenuation within the extra-axial hematoma, usually in epidural hematoma, seen on nonenhanced CT scan
• Represents an actively extravasating unclotted blood
• The area is surrounded by clotted blood (50-70 Hounsfield Units). Clotted blood is hyperdense on CT because of protein component of hemoglobin

Reference:

Al-Nakshabandi NA. The swirl sign. Radiology 2001; 218:433.

Leptomeningeal Enhancement

Sagittal T1W MR image post gadolinium shows extensive leptomeningeal enhancement (arrrows) along the cerebral sulci and cerebellar folia.

Differential Diagnosis:

• Leptomeningeal carcinomatosis: usually due to breast or lung metastasis, or primary CNS tumor. In children, the most common cause is medulloblastoma.
• Meningitis (bacterial, tuberculosis, coccidiodomycosis)
• Neurosarcoidosis: often involves the basal cistern

Facts: Leptomeningeal Carcinomatosis

• Hematogenous spread of malignancy (i.e., breast, lung) or direct extension by CNS tumor
• MRI with contrast administration best imaging tool to detect this abnormality, much more sensitive than CT
• Imaging Findings: smooth or nodular enhancement along the leptomeninges (extending into sulci), hyperintensity of sulci on FLAIR, hydrocephalus (which may be the only sign seen on CT)

Our case: Leptomeningeal carcinomatosis from esophageal cancer

References:

1. O'Brien WT. Top 3 differentials in radiology: a case review, 2009.

2. Lev MH, Heisserman J, Shetty S. Q&A color review of neuroimaging, 2008.

Cavernoma

Axial CT image shows a small well-defined hyperdense lesion (arrow) in the gray-white matter junction of the left posterior parietal lobe without evidence of mass effect or surrounding edema.

Axial T2W MR image shows the lesion predominantly high signal intensity with a complete ring of dark T2 signal, suggesting the presence of hemosiderin.

Facts: Cavernoma

• Low-flow vascular anomaly of the brain
• Endothelium-lined blood cavities without muscular or adventitial layers. No brain tissues present between these blood cavities
• May be sporadic, related to prior radiation, or hereditary
• Patients commonly present with seizures due to internal bleeding
• Annual bleeding rate between 0.25 to 0.7% per year
• On follow up, most cavernomas increase in size due to osmotic changes
• 80% are supratentorium, and size between 1-2 cm

Imaging

• Appearance depends on amount of internal thrombosis, hemorrhage and calcification
• MRI is the modality of choice because it can show various stages of bleeding in the lesion, which is characteristic for cavernoma
• If presents with acute hemorrhage, CT appearance will be similar to intracerebral hemorrhage of other causes. MRI in acute phase may provide a clue to the diagnosis of cavernoma if it shows various stages of bleeding in particular the presence of hemosiderin
• If presents incidentally, cavernoma appears as a hyperdense mass without causing mass effect on CT. If calcified, it will be only partially calcified. On MRI, it shows a complete ring of dark T2 signal due to the presence of hemosiderin (this effect is best seen on GRE T2* sequence)

Reference:

Kuker W and Forsting M. Cavernomas and Capillary Telangiectasias. In: Baert AL, Knauth M, Sartor K. Intracranial Vascular Malformations and Aneurysms, 2nd revised edition, 2008

Meningioma

Figure 1: Axial unenhanced CT image of the brain shows an isodense mass in the left posterior fossa with minimal, if any, mass effect.
Figure 2: Axial contrast-enhanced T1W MR image shows a large homogeneously enhancing extra-axial mass (star) near the left petrous bone overlying the sigmoid venous sinus (arrow).

Facts: Meningioma

• Tumors of meningeal cells (typically arising from meninges but can also be found in the choroid plexus, tela choroidea and arachnoid villi); therefore meningiomas can be seen in the meninges, spinal canal, intraventricular, and pineal regions
• Common, greater than 20% of all primary intracranial neoplasms
• Female:male = 3:2 to 2:1; mostly in late middle age
• Pathology: benign, atypical and malignant

Imaging Features

• Homogeneous, lobulated, well-circumscribed mass with uniform dense enhancement following contrast administration
• Common locations: parasagittal > convexity > sphenoid ridge
• High attenuation on unenhanced CT, iso- to mildly hypointense on T1W MR images
• May calcify in up to 1/4 of all cases, best seen on CT. Calcifications can be microscopic, punctate, large, peripheral or central. Malignant meningiomas rarely calcify.
• Hyperostosis can be seen in up to 1/2 of cases that meningiomas are immediately adjacent to the bone. Common in 'en plaque' meningioma
• Uncommon to have bone destruction (if pure destruction think of metastasis, sarcoma or myeloma)

Our case: benign meningioma overlying the sigmoid sinus without invasion. It is important to note if the meningioma is adjacent vascular structures for optimal surgical planning.

References:

1. Drevelegas A. Imaging of brain tumors with histological correlation, 2002.

2. DeAngelis LM, Gutin PH, Leibel SA. Intracranial tumors: diagnosis and treatment, 2002.

Sturge-Weber Syndrome

Axial CT images show "railroad track" calcifications (arrows) in the left occipital cortex with ipsilateral enlargement of the choroid plexus (arrowhead) in this patient with a port-wine stain in the left V1 distribution.

Facts

• Also known as encephalotrigeminal angiomatosis
• Sporadic disorder affecting skin and central nervous system
• Defined as capillary malformation of the leptomeninges with or without choroid and facial V1 or V1-V2 involvement (port-wine stain)
• Probably due to embryonic defect of persistent vascular plexus in the neural tube during 6th week of embryonic development
• Port-wine stains can be unilateral or bilateral, most commonly involve V1 distribution but can also be extracranial
• Intracranial involvement always ipsilateral to the port-wine stain of the face, occipital lobe most common

Imaging

• MRI more sensitive than CT in identifying secondary changes due to leptomeningeal capillary malformation
• Cerebral cortical atrophy, compensatory ventricular and choroid plexus enlargement, calvarial hemihypertrophy and superficial gyriform enhancement after gadolinium injection
• "Railroad track" calcification of the cerebral cortex caused by precipitation of calcium likely due to alternation of vascular dynamics of the leptomeningeal malformation

Reference:

Gorlin RJ, Cohen MM, Hennekam RCM. Syndromes of the Head and Neck, 4th ed, 2001.

Muller-Forell WS. Imaging of Orbital and Visual Pathway Pathology, 2005.

Primary CNS Lymphoma (PCNSL)

Axial T2W and postcontrast T1W MR images show two enhancing intra-axial masses (arrowheads) in the right cerebral hemisphere, involving the deep white matter. The frontal lobe mass crosses the midline at the corpus callosum (arrow), and is in contact with the ependyma.

Facts: PCNSL

• Rare, 1% of all primary brain tumors
• Incidence is rising in both HIV and non-HIV groups
• Uncertain origin because the CNS does not have endogenous lymphoid tissue or lymphatic circulation
• Three populations at risk: organ transplant recipients, patients with congenital immunodeficiency syndromes and AIDS/other immunodeficiency

Imaging

• Masses in deep gray matter structures, periventricular region and corpus callosum
• Up to 75% of masses are in contact with ependyma
• Enhancing homogeneously
• Some surrounding edema but less pronounced than gliomas or metastasis
• Do not calcify, rarely hemorrhage
• Imaging differential diagnosis: glioblastoma, metastasis, sarcoidosis

Our case: primary CNS lymphoma, non-Hodgkin type, in a non AIDS patient.

Reference:

Atlas SW. Magnetic Resonance Imaging of the Brain and Spine, Volume 1, 4th edition, 2008.