Vasculitis / Behcet disease

Findings

Figure 1, Figure 2, and Figure 3 demonstrate increased signal in the region of the bilateral basal ganglia, left thalamus, subthalamic region and brainstem. Diffusion-weighted images shows an area of restricted diffusion (Figure 2 and Figure).
Figure 4 shows contrast enhancement on T1WI in the left basal ganglia and focal meningeal enhancement.
Figure 5 single voxel MR spectroscopy within the region of interest demonstrates increased choline, slightly decreased NAA, and presence of lactate peak.
Figure 6, Figure 7, and Figure 8 Sagittal and axial T2 and axial T1 post contrast images show an abnormal long segment of high T2 signal in central cervical cord with subtle contrast enhancement.


Diagnosis: Vasculitis/Behcet disease


CNS vasculitis is a heterogeneous group of disorders characterized by nonatheromatous inflammation and necrosis of blood vessel walls. Arteries and veins are affected; it can involve intracranial vessels of any size.

A variety of systemic inflammatory diseases can cause vascular inflammation and stroke. Neuro-Behcet is a type of CNS vasculitis. Behcet disease is a chronic, relapsing, inflammatory disease characterized by presence of recurrent and usually painful mucocutaneous ulcers, genital lesions, ocular lesions, neurologic manifestations and cutaneous manifestations. Behcet is uncommon in the United States.

Neurologic manifestations are seen in approximately 10-25% of patients with Bechet disease. CNS manifestation results from arterial or venous thrombosis. Neuro-Behcet disease (NBD) usually shows three clinical patterns: A brainstem syndrome, a meningomyelitic syndrome and an organic confusion syndrome.

The typical MRI findings are multiple focal T2 signal abnormalities, restricted diffusion in the acute phase of disease, and patchy vascular and leptomeningeal enhancement. The most common site of involvement is the brainstem, followed by white matter, internal capsule and basal ganglia or thalamus. Brainstem atrophy is one of the manifestations of chronic NBD. Meningeal involvement is a less frequent finding. Follow up studies show change in site, size and shape of the lesions. Cerebral venous thrombosis is seen in approximately 0.6 to 10% of Behcet disease. The spinal cord involvement is rare. It usually shows long segment lesions demonstrating high signal in T2 WI, which may show patchy enhancement. Thoracic and cervical cords are usual sites of involvement.

In the largest series to date, the clinical features and outcomes of 200 patients with Behcet disease and neurologic involvement were reported. On average, a period of approximately 5 to 6 years elapsed between the onset of the earliest non-neurologic symptoms of Behcet disease and the appearance of neurologic symptoms or findings. In a small percentage of Behcet, neurologic findings may appear concurrently or precede non-neurologic features.

The prognosis varies with the type of neurologic process. Those with dural venous thrombosis or other non-parenchymal processes are less likely to have recurrent disease, disability, or premature death. By comparison, patients with parenchymal disease have a worse outcome.

CPPD of the cervical spine - "crown dens syndrome"

Findings

Figure 1: Sagittal view from a CT of the cervical spine utilizing a bone algorithm demonstrates a well-defined subchondral cyst in the odontoid process associated with partially calcified retro-odontoid soft tissue. There is also an erosion of the C5 spinous process as well as a fluid collection interposed between the spinous processes of C4 and C5. Calcification of the C2/C3 intervertebral disc is also noted. There is also minimal calcification of the longus colli.

Differential for crystal arthropathies that involve the cervical spine include
- CPPD
- Hydroxyapatite deposition disease
- Gout
- Other (rare)


Diiagnosis: CPPD of the cervical spine - "crown dens syndrome"


CPPD (calcium pyrophosphate deposition disease) is one of the entities known to cause crystal deposition in cartilage. It is most commonly found to be idiopathic, but other etiologies include a hereditary autosomal dominant condition, hyperparathyroidism, and hemochromatosis. While the classic locations for CPPD include the triangular fibrocartilage of the wrist, menisci of the knee, and pubis symphysis, the spine can also be involved. CPPD crystal deposition can be found in several structures of the spine including the ligaments, intervertebral discs, joint capsules, and synovium.

CT is the best modality to see the various calcific deposits in the cervical spine, while MRI is usually used to evaluate for spinal cord compression or myelopathy. Imaging findings include calcification of the intervertebral disc as well as disc space narrowing, “vacuum phenomena,” and vertebral sclerosis. Calcification in the periodontoid tissue in association with acute neck pain has been coined the “crown dens syndrome.” In addition to this acute symptomatology, these calcifications, particularly in the retro-odontoid region, can eventually lead to neurologic compromise from mass effect in the form of ventral cervicomedullary compression in the elderly. Deposition within the joints, such as the atlantoaxial and facet joints, can lead to erosions, subchondral cysts and pathologic fractures. CPPD deposits in the spinal ligaments can cause either a focal or diffuse enlargement of the ligaments and cause spinal stenosis.

The differential for calcific deposits in the cervical spine is a limited one. Hydroxyapatite deposition disease (HAAD) can present with periodontoid calcifications and can be indistinguishable from CPPD on CT. Patient history and, ultimately histological analysis of the crystals, help differentiate between the two. HAAD can also present as a calcific tendonitis with calcifications in the longus colli muscles, usually at the C1-C2 level. The inflammatory response to the CPPD deposits in the intervertebral disc space can be aggressive enough to mimic a discitis. Correlation with the patient’s clinical history would be helpful. In difficult cases, a biopsy may be needed. Gout can cause similar findings as CPPD including erosions of the cervical osseous elements, including the odontoid process, as well as mimic a discitis. Gout’s main imaging findings include erosions and proliferative osseous changes. Clinical history and/or crystal analysis may be needed for definitive diagnosis.

Meningioma

Findings

CT shows a large circumscribed vertex mass in the right parietal region with heterogeneous hyperdensity and calcification. There is significant vasogenic edema and minimal if any mass effect or midline shift.
MRI from next day shows broad attachment of the lesion to the dura with moderate contrast enhancement. T2 prolongation compatible with vasogenic edema is again present.

Differential diagnosis:
- Meningioma
- Metastatic disease with hemorrhage and/or calcification
- GBM
- Low grade astrocytoma
- Angiosarcoma
- Tuberculoma


Diagnosis: Meningioma


Discussion

Meningiomas are thought to arise from arachnoid cap cells and may arise in the spinal cord or intracranially. Fewer than 10% are symptomatic. They may present with headache, seizure, or focal neurologic signs due to cranial nerve or brain parenchymal compression or vascular compression. Known causes include radiation and genetic abnormalities (including a relationship to NF2). Other causes are speculated as well. Meningiomas are generally considered benign tumors. However, a few histologic types can break this rule and invade cortex and even metastasize. Therapy includes conventional surgery and radiosurgery. Chemotherapy can be used following resection. Angiography is often performed for surgical planning and occasional embolization.


Radiologic overview of the diagnosis

Plain films of the skull may demonstrate hyperostosis and increased vascular markings. CT and MRI demonstrate extra axial, dural based lesions. Meningiomas typically enhance homogeneously and may have an enhancing dural tail (which may be more evident on coronal or sagittal MRI depending on the location)..On CT, the lesion may be isoattenuating to hyper attenuating but may contain calcifications. Vasogenic edema will likely be present and may be more apparent on MRI. T1 and T2 signal is variable. MR spectroscopy demonstrates a high alanine peak. Buckling of the cortex (seen in this case) is strongly suggestive of an extra axial lesion and should narrow the differential diagnosis. Other clues to extra axial location are brain cysts and trapped CSF. Angiographic findings include a sunburst vascular pattern and "mother-in-law" blush (comes early and stays late).

Intracranial chondrosarcoma

Findings

Figure 1: Sagittal T1 demonstrates a low-signal mass centered in the sphenoid bone and extending into the anterior cranial fossa. The pituitary and suprasellar cistern are preserved.
Figure 2: Coronal T2 image shows displacement of the frontal lobes without brain edema confirming extra-axial location. The mass is high signal on T2 images which is non-specific but typical of chondrosarcoma. There is edema in and around both optic nerves.
Figure 3 and Figure 4: T1 weighted fat-suppressed post gadolinium axial and coronal images demonstrate avid enhancement of the solid mass.
Figure 5 and Figure 6: Axial and coronal CT demonstrate the calcified matrix within the mass taking characteristic “ring and arc” shapes. The anterior and superior walls of the sphenoid sinus are eroded confirming the aggressiveness of the tumor.

Differential Diagnosis:
- Chondrosarcoma
- Meningioma
- Chordoma
- Metastasis
- Lymphoma


Diagnosis: Intracranial chondrosarcoma


Intracranial chondrosarcoma is a slow-growing, locally invasive, rare malignant neoplasm of cartilaginous origin which accounts for 0.15% of all intracranial tumors and most commonly affects the skull base. Often when encountered, other anterior skull base malignancies, such as meningioma, metastasis, chordoma, rhabdomyosarcoma, and lymphoma may be difficult to distinguish. However, recognizing the range of appearances of intracranial chondrosarcomas on various imaging modalities along with clinical, gross, and histological studies may allow for improvement in the diagnosis, evaluation, and management of this malignancy.

Primary chondrosarcoma is divided into multiple variants, depending on the location and histological characteristics. These include conventional, clear cell, myxoid, mesenchymal, extraskeletal, and dedifferentiated. Skull base chondrosarcomas are most commonly of the conventional type and occupy areas that include petrosal bone, temporoccipital bone, clivus, sphenoethmoidal complex, and less commonly the frontal, parietal, and ethmoidal bones. Conventional chondrosarcomas can be further classified into histological subtypes of grade I, grade II, and grade III, with grade I demonstrating the least malignant and aggressive potential. The mesenchymal variant is the most malignant of all types and typically presents in a younger population. This type has a predilection for dural and cerebral extension.

Intracranial chondrosarcomas have been shown to be minimally sensitive to conventional radiation therapy, thus requiring radical excision of the tumor for effective management. Therefore, diagnostic imaging with MRI and CT is significant for neurosurgical assessment of tumor invasion and its anatomic orientation with any surrounding vascular, bony, and neural structures. Radiological imaging has enhanced diagnosis as CT is useful in finely delineating tumor invasion, bony invasion, and abnormal “ring and arc” or stippled calcification typical of chondrosarcomas. The tumor is normally isoattenuated or hyperattenuated with some degree of heterogeneous enhancement. MRI with gadolinium allows for evaluation of significant vessels and nerves such as the carotid arteries and optic nerves that lie in the preferred area of tumor growth. Furthermore, the tumor appears with decreased signal on T1 weighted images and increased signal on T2-weighted images. MRI enhancement will be mild to moderate, typically described with a “honey-combing” appearance due to islands of cartilage. In addition, it has been demonstrated that there is only mild edema surrounding chondrosarcomas in contrast to other skull base malignancies. MRI perfusion has also been documented to be effective in differentiating chondrosarcomas from other anterior skull base malignancies by assessing the cerebral blood volume and perfusion. Tumor vascularity is variable depending on the histological type; however, conventional and mesenchymal chondrosarcomas are commonly hypovascular, which differentiates it from the significantly vascular meningioma and metastatic lesion.

Although rare, intracranial chondrosarcomas should be considered in the differential diagnosis of any skull base malignancy that causes cranial nerve deficits. Clinically, patients commonly present with headaches, tinnitus, dizziness, decreased sense of hearing, visual symptoms such as diplopia and other oculomotor disorders depending on the location of the mass. The mean age of patients with intracranial chondrosarcomas has been reported to be 37 without any gender predilection. Although conventional radiation has limited indication, there has been considerable debate regarding optimal treatment with proton radiotherapy in combination with surgical excision. The difficulty in evaluating the outcomes of these various treatment strategies for skull base chondrosarcomas stems from the fact that this is a rare malignancy.

Sturge-Weber syndrome

Findings

Gyriform calcifications are observed over the left occipital lobe in the CT exam. The MRI demonstrates atrophy of the left cerebral hemisphere. There is enlargement of the left choroid plexus which demonstrates homogeneous enhancement post contrast. There is also gyriform enhancement post contrast most significantly on the left occipital lobe. There is diffuse enhancement of the subcutaneous tissues over the left eye.


Diagnosis: Sturge-Weber syndrome


Key points

Classically the patients have a facial port-wine stain, ipsilateral intracranial abnormalities, contralateral hemiparesis, hemiatrophy, mental retardation, and homonymous hemianopia. The severity of these features varies widely patient to patient. Commonly the patients will have glaucoma on the affected side. Seizures are also very common.
Only 8% of patients with port-wine stains have Sturge-Weber Syndrome. 13% of Sturge-Weber syndrome patients do not have a facial angioma.
There is no clear genetic link at this time. There is no sex or race predilection and it is very seldom seen more than once in the same family. Several different chromosomal abnormalities have been implicated.
Radiographically one can see "tram track calcifications" which are leptomeningeal calcifications like those seen on the CT image.
MRI can demonstrate the angiomatous abnormalities. In this case the cutaneous capillary angioma (port-wine stain) is well demonstrated as is the meningeal angiomatosis over the left occipital lobe. Cerebral hemiatrophy is well demonstrated by MRI as is the choroidal angiomatosis.
Multiple therapies are employed in these patients. The port-wine stains can be "removed" with laser treatments. Seizures can be treated with anticonvulsants. Refractory seizures can be treated surgically. The surgeries can be as extensive as a hemispherectomy.

Acute necrotizing encephalitis (ANE)

Findings

Figure 2: Axial T2-weighted image showing bilaterally symmetric hyperintensity in the thalami. Note the target appearance of the lesions.
Figure 3: Axial T2-weighted image showing bilaterally symmetric hyperintensity in the dorsal pons.
Figure 4 and Figure 5: Coronal FLAIR images showing bilaterally symmetric hyperintensity in the thalami and dorsal columns.


Diagnosis: Acute necrotizing encephalitis


Acute Necrotizing Encephalitis (ANE) characteristically occurs in children after a mild antecedent illness. The peak age of incidence is six to eighteen months, however, ANE can occur in older children as well (the patient in this particular case was nine years old). Typically, the patient will present within a few days of a mild illness (e.g. fever and/or upper respiratory infection) with seizures, decreased level of consciousness, and/or vomiting.

Pathologic evaluation of the lesions demonstrates necrosis (due to severe edema) in the thalami, tegmentum, and dentate nuclei. In addition to necrosis, there is florid petechial hemorrhage around small parenchymal vessels. Pathologically, ANE is differentiated from ADEM by the lack of inflammatory cells found in ANE, as opposed to the presence of lymphocytes in ADEM. In addition to characteristic lesions of the thalami, tegmentum, and dentate nuclei; about one half of those affected will also have patchy lesions in the cerebral white matter (similar in appearance to ADEM). Unlike the thalamotegmental lesions, the patchy cerebral white matter lesions of ANE are not hemorrhagic. The presence of hemorrhage in patchy cerebral white matter lesions instead suggests the diagnosis of Acute Hemorrhagic Encephalomyelitis, which is distinct from ANE and ADEM.

Imaging studies in ANE typically show bilaterally symmetric lesions of the thalami, which may extend to the lateral putamina and external capsule, as well as tegmentum and cerebellar nuclei. The lesions are often necrotic and hemorrhagic. Ring-enhancement around the areas of hemorrhage and necrosis can be seen within a few days of onset. Initially, on diffusion-weighted imaging (DWI), the lesions exhibit restricted diffusion due to cytotoxic edema (restricted diffusion results in increased signal intensity on DWI). As necrosis develops, the movement of water molecules is less restricted (and ultimately unrestricted, as cell membranes dissolve), resulting in decreased signal intensity in areas of necrosis on DWI. Magnetic susceptibility artifact, secondary to hemosiderin deposition, may also contribute to the hypointensity seen in the center of the lesions on DWI; however, depending on the type of DWI employed, magnetic susceptibility artifact is probably less of a factor than decreased restriction of diffusion due to necrosis.

Terson syndrome

Findings

Figure 1 and Figure 2: Axial noncontrast head CT demonstrates hyperdensity within the basal cisterns and sylvian fissures indicating diffuse subarachnoid hemorrhage.
Figure 3: Axial noncontrast CT with attention to the orbits demonstrates lentiform hyperdensity layering along the posterior aspect of the globes.


Diagnosis: Terson syndrome


Terson syndrome is defined by the presence of retinal, vitreous or any intraocular hemorrhage in association with subarachnoid hemorrhage. Several theories have been proposed with regard to its development. The most common theory suggests that raised intracranial pressures associated with subarachnoid hemorrhage leads to ocular venous outflow obstruction, thereby resulting in ocular hemorrhage. The hemorrhage is usually bilateral and composed of hyperdense crescentic collections along the posterior globe, near the optic nerve head. Other entities such as melanoma, metastatic lesions, and hemangiomas are in the differential, however in the setting of subarachnoid hemorrhage, Terson syndrome should be strongly considered.

Once findings of intraocular hemorrhage are noted, ophthalmologic consultation should be requested in order that a detailed fundoscopic exam be performed. Establishing a baseline is important to follow the progression or regression of the hemorrhage. Most hemorrhages clear spontaneously, however in those that do not, a vitrectomy may be needed to preserve vision.