mercoledì 28 dicembre 2005
Hemorrhagic Rathke's cleft cyst
There is expansion to the sella (Figure 1). No associated calcification is seen.
MR images demonstrate a lesion that is cystic and contains a fluid-fluid level with signal characteristics consistent with internal hemorrhage (Figure 4); the dependent fluid has signal characteristics consistent with acute blood. No nodularity or internal soft-tissue component is seen. The lesion exerts mass effect upon the optic chiasm, displacing it superiorly (Figure 3 and Figure 4). The infundibulum is displaced superiorly and anteriorly. The wall enhances (Figure 5 and Figure 7); there is no internal enhancement. There is no cavernous sinus invasion.
Diagnosis: Hemorrhagic Rathke's cleft cyst
In this case, craniopharyngioma was felt to be less likely since a high percentage of these calcify and typically display thick-walled, solid, or nodular enhancement. Macroadenoma was felt to be less likely due to lack of cavernous sinus invasion and the uniformly thin wall of this lesion.
Rathke’s cleft cysts are often asymptomatic, but can enlarge and compress pituitary gland, hypothalamus, or optic tract.
Most common symptoms: hypopituitarism, visual disturbance, and headache.
MRI appearance is variable; contents of cyst can be either simple or complex, secondary to blood or mucinous material. Thin wall may enhance, secondary to squamous metaplasia or peripherally displaced rim of pituitary tissue. Calcification is rare.
giovedì 22 dicembre 2005
Sagittal T1-weighted contrast-enhanced image shows a mass in the cervical region, which enhances at the level of C4 and at C5-6 (Figure 1). On these images alone, it is difficult to differentiate from nonenhancing soft tissue; but, there are three complex cysts, which are hyperintense to CSF - above, below, and between the areas of enhancement (Figure 1). There is also a dilated intramedullary cyst below the fourth ventricle, which is of CSF intensity (Figure 1).
The sagittal T2-weighted images of the cervical and thoracic spine show hemosiderin staining with a “cap sign” at the superior margin at the level of C4 and the inferior margin at the level of T3-4 (Figure 2 and Figure 3) of the tumor. There is hemorrhage superiorly in complex cysts (Figure 2). There is also an intratumoral cyst (Figure 2 and Figure 3).
Diagnosis: Spinal ependymoma
Ependymomas are the most common intramedullary spinal cord tumor in adults. The highest incidence is seen in the third through fifth decades of life. Patients sometimes are given a delayed diagnosis because of the mild nature of symptoms which can be chronic in nature. Most commonly, the symptoms are neck and back pain with sensorimotor symptoms, and bowel and bladder incontinence being less frequent. These tumors arise from ependymal cells lining the canal and are usually histologically benign. Ependymomas are well circumscribed, often surrounded by a thin delicate capsule, and are noninfiltrating. Frequently, areas of necrosis and hemorrhage are present in these tumors.
In the spinal cord, ependymomas most commonly occur at the level of the cervical spine (44%), sometimes extending to the upper thoracic spine (additional 23%). Less commonly, these tumors involved the thoracic cord alone or the conus medullaris. Most ependymomas are hypointense to isointense to spinal cord on T1-weighted images. There may be focal T1 hyperintense areas corresponding to areas of hemorrhage. On T2-weighted sequences, these spinal cord tumors demonstrate high signal in cystic areas with up to one-third containing the "cap sign" of hypointense signal representing a hemosiderin at the rostral and caudal margins. In addition, ependymomas are commonly seen to enhance with contrast. Usually, there is associated cord edema present. A subtype, myxopapillary ependymoma, is seen in the filum terminale and subcutaneous sacrococcygeal region which appears multilobulated and encapsulated.
Prognosis is generally good with a 5-year survival of 82%. The treatment of choice is microsurgical resection with radiation therapy given for incomplete resection, recurrence, or disseminated disease. Metastatic disease can be seen in the lungs, retroperitoneum, and lymph nodes.
martedì 13 dicembre 2005
Glomus vagale tumor
Figure 1 demonstrates a large, intensely-enhancing, heterogeneous left-sided carotid space mass displacing the internal carotid artery (ICA) medially, the external carotid artery (ECA) and its branches antero-medially, and the internal jugular vein (IJV) postero-laterally.
Figure 2 demonstrates anterior displacement of the parapharyngeal fat by the glomus vagale tumor.
Figure 3 demonstrates anterior displacement of the ICA by the left-sided fusiform-shaped glomus vagale tumor.
Figure 4 demonstrates antero-medial displacement of the ICA and posterior displacement of the IJV by the glomus vagale.
Figure 5 with arrows pointing to multiple flow voids within the left carotid space mass.
Diagnosis: Glomus vagale tumor
Paragangliomas account for only 0.6% of all neoplasms of the head and neck. They arise from the paraganlgia or glomus cells, which are part of the extra-adrenal neuroendocrine system, and are named for the paraganglia from which they arise. The four most common sites for paragangliomas of the head and neck are the carotid body (carotid body tumor), the jugular foramen (glomus jugulare), along the path of the vagus nerve (glomus vagale) and in the middle ear (glomus tympanicum). Paragangliomas are characteristically vascular, intensely enhancing lesions that demonstrate low T1 and high T2 signal with multiple flow voids. The "salt-and-pepper" appearance has been named for the T2 appearance, as the high T2 signal of the tumor is the "salt" and the multiple flow voids the "pepper".
Paragangliomas can be distinguished from each other primarily based on their location. The carotid body tumor typically splays the common carotid bifurcation, while the glomus vagale displaces both the ECA and ICA antero-medially away from the IJV. Glomus jugulare tumors characteristically expand and erode the jugular foramen causing the characteristic "moth-eaten" appearance. The glomus tympanicum is a small discrete mass arising from the cochlear promontory in the middle ear.
The current primary treatment modality is surgery with possible pre-operative embolization; radiation is reserved for non-resectable and recurrent cases and those invading the ICA. Paragangliomas have a high (40%-50%) rate of local recurrence, can be locally aggressive with intra-cranial extension (20%), and can behave in a malignant manner (2%-13% metastasize to lung, bones and lymph nodes). Familial paragangliomas (7%-9% of cases) are more commonly multiple (1/3) than sporadic cases (5%), and occur at a younger age. The primary differential diagnosis for a carotid space mass is: nerve sheath tumors, nodal metastasis (renal and thyroid cancer), abscess, and venous thrombosis.
Etichette: ACR, Head - Neck, Neoplasm
mercoledì 7 dicembre 2005
Axial CT shows elongated and thickened superior cerebellar peduncles. Note hte "bat-wing" appearance of the fourth ventricle.
Axial T2-weighted image (Figure 2) through again demonstrates characteristic "bat-wing" appearance of the fourth ventricle with enlarged superior cerebellar peduncles.
Axial T1-weighted inversion recovery image (Figure 3) at the level of the cerebellar peduncles again shows the enlarged superior cerebellar peduncles. The isthmus of the brainstem (the transitional zone between the pons and midbrain) is small and in combination with elongated thickened superior cerebellar peduncles produces the "molar tooth sign." Note the cerebellar hemispheres are in apposition without evidence of fusion.
Mid-sagittal T1-weighted MR (Figure 4) confirms absence of the cerebellar vermis.
Coronal T2-weighted image (Figure 5) shows the thickened cerebellar peduncles (Figure 5) and absence of the normal vermis, without cerebellar hemispheric fusion.
Diagnosis: Joubert syndrome
Joubert syndrome is an autosomal-recessive disorder, characterized by clinical presentation of hypotonia, ataxia, and global developmental delay. A variety of other abnormalities have been described in affected children, primarily episodic hyperpnea, abnormal eye movements, and a characteristic facial appearance. The phenotype may vary even among siblings with Joubert syndrome.
From an imaging perspective, these patients have either complete or partial agenesis of vermis, which results in triangular-shaped mid fourth ventricle and a bat-wing appearance in its superior aspect. The cerebellar hemispheres oppose one another in the midline due to absence of vermis. The isthmus and the midbrain are small in AP diameter, likely secondary to absence of decussation of the superior cerebellar peduncles. This appearance of small brainstem with elongated and thickened superior cerebellar peduncles has been termed the molar tooth sign. It has been proposed that both the superior cerebellar peduncles and the corticospinal tracts remain uncrossed in these patients. The classic imaging findings are, however, not completely specific for Joubert syndrome and have been found recently in a number of very rare congenital syndromes.
Etichette: ACR, Genetic-Metabolic, Neuro, Pediatric
mercoledì 23 novembre 2005
Thin section CT at the level of the right and left middle ear cavity. There is opacification of the right middle ear cavity and right mastoid air cells (Figure 1). Note that the left middle ear cavity and mastoid air cells are well aerated (Figure 2).
Thin section CT demonstrates opacification of the right petrous apex (Figure 3).
Axial SPGR and FLAIR. Low- and high-signal intensity in the right mastoid air cells and right petrous apex, respectively (Figure 4 and Figure 5).
Axial T2. Abnormal high signal in right mastoid air cells and petrous apex (Figure 6).
Post-contrast. There is enhancement within the right petrous apex and mastoid air cells (Figure 7).
Post-contrast. Image at a slightly higher level than prior image demonstrates an enhancing process with extention to the dura of the middle cranial fossa and the prepontine region (Figure 8).
Diagnosis: Gradenigo syndrome
Petrous apicitis is a rare complication of otitis media or mastoiditis, in which infection, most commonly by pseudomoas, spreads to the petrous apex. Extension of the infection into Dorello's canal, through which pass CN VI and CN V, results in abducens nerve palsy and deep facial pain, termed the Gradenigo syndrome or triad. Extradural abscess, osteomyelitis, cavernous sinus thrombosis, or meningitis can complicate matters in more severe cases. Surgery may be indicated if a focal abscess has developed and the patient is unresponsive to antibiotics.
CT findings include opacification of the ipsilateral mastoid air cells and bony erosion of the petrous apex. Apicitis generally does not enhance, however, cavernous sinus enhancement may be seen. Typical MR findings of acute apicitis include low T1 signal and high T2 signal with rim enhancement. Chronic cases show high T2 signal with variable enhancement. Differential considerations include malignancies such as epidermoid tumors and metastatic disease. Other lesions of the petrous apex include cholesterol granuloma, cholesteatoma, eosinophilic granuloma, chordoma, and meningioma; however, each of these entities demonstrates unique imaging characteristics. The radiographic findings of petrous apicitis in the appropriate clinical context are diagnostic.
Etichette: ACR, ENT, Infectious
venerdì 18 novembre 2005
Lymphoma invading neuroforamina with cord compression
Axial T2 image (Figure 1) reveals a mass extending through the right neural foramina with obliteration of the CSF space and displacement and narrowing of the cord.
An axial T1 post-contrast image (Figure 2) demonstrates enhancement of the mass as it enters the right neural foramina.
Sagittal T1 post-contrast image (Figure 3) depicts a large enhancing epidural mass causing significant narrowing of the spinal canal. Diffuse heterogeneous enhancement of the visualized vertebral bodies is consistent with bone marrow involvement by tumor.
Diagnosis: Lymphoma invading neuroforamina with cord compression
Acute spinal cord compression is a potentially devastating neurological emergency that requires both prompt diagnosis and intervention to prevent permanent impairment. The frequency of metastatic cord compression is increasing as cancer prevalence rises and new treatment modalities prolong patient survival. Approximately 5% of patients with terminal cancer develop epidural spinal cord compression. Metastases are 25 times more common than primary tumors as a causative etiology. Intramedullary spinal cord metastasis have frequency of 1/16 that for epidural metastasis and are best diagnosed by MRI. Of note, approximately 20% of patients with spinal cord compression have the associated new neurological deficits as their initial manifestation of disease.
Many types of tumor metastasize to the epidural space. Relative incidence of spinal cord compression by a particular type of tumor is determined by a combination of tumor prevalence in the population and its predilection for spinal involvement. In adults the most common tumors causing cord compression are prostate, breast, lung, NHL, multiple myeloma, renal, and colorectal cancer. In children the most common types are germ cell tumors, Hodgkin's, and sarcomas, especially Ewing's. Lymphoma may classically extend through the neuroforamina into epidural space to cause spinal cord compression.
Information from the neurological exam is critical for localization of the lesion and optimization of the MRI protocol. Whole spine imaging is generally undesirable as it is more time-consuming, expensive, and difficult for patients who are often in considerable pain. It further lowers resolution on exams that are often suboptimal secondary to severe patient pain and patient movement. Spinal sensory levels on neurological examination may be up to several segments below the anatomic level of cord compression. Evaluation of motor function and reflexes is very useful for lesion localization. Pain is ubiquitous in cancer patients, and while it may be initially localized, it is not specific to cord compression and is more often related to vertebral metastasis and pathologic fracture. Pain increases in intensity with worsening compression. Pain from cord compression often worsens with recumbency.
Once the site of interest is more precisely identified, sagittal T1 and T2 images and axial T2 images are required for the diagnosis. Axial T1 images through the lesion may then be obtained for further characterization of the anatomy and evaluation of hemorrhage. Spinal cord compression may be defined on imaging as the presence of a mass lesion abutting the cord with the complete loss of intervening CSF. This must be accompanied by deformation of the spinal cord, and/or the presence of signal changes within the cord. The findings are best visualized on T2-weighted images. In the case of neoplasm, intravenous contrast may be useful for further characterization. However, intravenous contrast is not necessary for the diagnosis of acute cord compression.
giovedì 10 novembre 2005
Spinal epidural hematoma
Lateral radiograph of post-operative day 3 demonstrates significant prevertebral soft tissue swelling and gas that is intervally worse from prior radiograph (Figure 1).
Lateral radiograph following emergent reexploration demonstrates interval improvement in prevertebral soft tissue swelling and gas collection (Figure 2).
Sagittal T2-weighted images (SE Figure 3, FLAIR Figure 4, and STIR Figure 5) demonstrate a focal collection, hypointense on SE and STIR and isointense on FLAIR anterior to the cord. The collection extends from C3 to C5 (Figure 3, Figure 4, and Figure 5). The cord is compressed and displaced posteriorly.
Axial T2-weighted image of the cervical spine at the level of the inferior endplate of C2 demonstrates a preserved canal with no compression upon the cord (Figure 6).
Axial T2 and axial gradient images demonstrate a collection ventral to the cord with significant cord compromise (Figure 7 and Figure 8).
Diagnosis: Spinal epidural hematoma
Spinal epidural hematoma is being increasingly recognized on magnetic resonance imaging (MRI) in the setting of trauma. Most studies note a male dominance and a reported mean age of 41-52 years. Many causative factors have been implicated including trauma, coagulopathies, rupture of arteriovenous malformations, vertebral body hemangiomas, hypertension, and pregnancy.
Presenting symptoms often include acute radicular pain and rapid onset of paraplegia. The appearance on CT is usually a high-attenuation lesion, which can present both posterior and anterior to the cord. MR is the imaging modality of choice because of excellent soft-tissue contrast resolution, the ability to survey large regions of the spine, and the ability to determine the degree of thecal sac and spinal cord compression. The MR appearance is variable but most commonly is iso- to slightly hyperintense on T1-weighted sequences in comparison to spinal cord, and hyperintense with areas of hypointensity on T2-weighted sequences. Gradient imaging is invaluable in the setting of suspected epidural hematoma because if its excellent ability to delineate blood and blood products.
This case represents a classic appearance of a post-surgical spinal epidural hematoma, which is rarely encountered, and was proven surgically with emergent evacuation secondary to progressive symptoms of weakness.
giovedì 3 novembre 2005
There are enhancing subependymal nodules (Figure 3) with the largest having degenerated into a subependymal giant cell astrocytoma (Figure 1 and Figure 2). There are multiple cortical/subcortical tubers seen best on FLAIR images (Figure 4).
Diagnosis: Tuberous sclerosis
Tuberous sclerosis is an autosomal dominant, inherited disorder that affects cell differentiation, proliferation, and migration. The classic clinical triad includes epilepsy, mental retardation, and cutaneous skin lesions. Almost all organ systems are affected including cutaneous, neurologic, ocular, dental, pulmonary, and cardiac.
Diagnostic criteria include major and minor features. Definite diagnosis requires at least 2 major features or 1 major with 2 minors.
Major features include
- facial angiofibromas
- shagreen patches
- ash-leaf spots
- subependymal nodules
- subependymal giant cell astrocytoma
- cardiac rhabdomyoma
- renal angiomyolipoma
- retinal hamartoma
Minor features include
- dental pits
- renal cysts
- rectal hamartoma polyps
- cerebral white matter migration lines
- gingival fibromas
- confetti skin lesions
Characteristic neurologic findings are present in over 95% of patients diagnosed with tuberous sclerosis. The classic neurologic features are calcified subependymal nodules, subependymal giant cell astrocytomas, cortical and subcortical tubers, and white matter lesions along lines of neuronal migration. Subependymal nodules can progress into subependymal giant cell astrocytomas that can result in obstructive hydrocephalus at the foramen of Monro. Subependymal nodules and subependymal giant cell astrocytomas usually enhance on contrast studies and are often found along the caudothalamic groove. Periodic brain CT or MRI with contrast can be performed in asymptomatic patients to evaluate for development or progression of lesions that may eventually result in obstructive hydrocephalus. MRI fluid-attenuated inversion recovery (FLAIR) sequences are better for evaluation of subcortical and cortical tubers.
Other imaging studies to consider include ultrasound to evaluate for renal angiomyolipomas or renal cysts, as well as cardiac CT or echocardiogram to evaluate for rhabdomyoma.
Treatment mainly focuses on minimizing the patient’s seizure activity by using anti-epileptic medications and a ketogenic diet.
Etichette: ACR, Genetic-Metabolic, Neuro, Pediatric
giovedì 27 ottobre 2005
MR findings include serpiginous high and low signal (depending on flow rates) within feeding and draining vessels (Figure 1 andFigure 3). High T2 signal can be seen in the adjacent brain parenchyma secondary to gliosis, edema, or ischemia, as is seen in this case (Figure 3).
MRA reveals AVM with feeding artery branching from the left PCA. Nidus and tangled vessels are visualized (Figure 4).
Diagnosis: Arteriovenous malformation
Cerebrovascular malformations are divided into 4 major categories including arteriovenous malformation, venous angioma, capillary telangiectasia, and cavernous angioma. AVMs can be visualized with angiography, computed tomography, or magnetic resonance imaging. AVMs are the most common symptomatic vascular malformation and occur in about 0.1% of the general population. The clinical presentation is variable, including headache, seizure, and focal neurological deficits. They are occasionally discovered as an incidental finding.
AVMs are a direct communication between arterial and venous circulations and consist of a nidus of tangled dilated vessels. There are 3 subtypes that depend on the blood supply: these are pial, dural, and mixed pial-dural types. Aneurysm is associated with the feeding arteries in approximately 10% of cases. Arteriovenous shunting is usually rapid so that most vessels appear as flow voids. An AVM replaces normal brain tissue without causing mass effect, unless complicated by hemorrhage and edema. Adjacent parenchymal atrophy is common secondary to vascular steal and ischemia.
3-D TOF MRA can be diagnostically useful in demonstrating feeding arteries, the nidus, and draining veins. Occasional pitfalls in MRA evaluation include signal void in tortuous vessels, nonvisualization of draining veins resulting from spin saturation, and difficulty with differentiation of blood flow from blood clot. Conventional angiography may be necessary for treatment planning.
Etichette: ACR, Malformations, Neuro, Vascular
mercoledì 26 ottobre 2005
Thyroglossal duct cyst
Figure 1 demonstrates a cystic mass embedded in the strap muscles of the neck. Tract of thyroid tissue between cystic mass and thyroid gland is seen (Figure 2and Figure 3).
Diagnosis: Thyroglossal duct cyst
Thyroglossal duct cyst is the most common congenital neck mass and accounts for 70% of congenital neck abnormalities. Most patients present in the second decade with an enlarging, painless mass. Thyroglossal duct cysts are located in the midline (75%) or slightly off midline (25%), however, they are always within 2 cm of midline. Most cysts are located either at (15%) or below (65%) the level of the hyoid bone. On CT, the cysts usually appear as a smooth, well-circumscribed mass with a thin wall and homogeneous attenuation, measuring fluid in attenuation. Elevated attenuation levels may reflect increased protein content and can correlate with history of prior infection. Peripheral rim enhancement is usually observed on contrast-enhanced scans.
Thyroid gland development begins in the third week of fetal life as a median outgrowth from the primitive pharynx at the level of the foramen cecum, which lies at the junction of the anterior two thirds and posterior one third of the tongue. The primitive thyroid descends in the neck and passes anterior to the hyoid bone and laryngeal cartilages. The gland reaches its final position in the inferior part of the neck by the seventh week after descending anterior to the thyrohyoid membrane and strap muscles. During the migration, the analage of the thyroid gland is connected to the tongue by a narrow tubular structure, the thyroglossal duct. This structure usually involutes by the eighth to tenth week of gestation. If any portion of the duct persists, secretions from the epithelial lining may give rise to cystic lesions.
The differential diagnosis includes obstructed laryngoceles and branchial cleft cysts. Laryngoceles are dilated laryngeal saccules. They may appear as a well-defined smooth mass in the lateral aspect of the superior paralaryngeal space. They may occur deep to the strap muscles, however, they arise within the larynx and can be visualized to connect back to the larynx. Failure of complete obliteration of an embryonic branchial cleft in the eighth to ninth week of fetal development results in a branchial cleft cyst, 95% of which derive from the second branchial cleft. Branchial cleft cysts usually manifest in the young adult as a mass near the mandibular angle (submandibular space), however, they can occur anywhere along the residual cleft tract extending from the suprclavicular region to the tonsillar fossa. Typically, the cyst is a round or oval mass that displaces the sternocleidomastoid muscle posteriorly or posterolaterally, the carotid artery and internal jugular vein medially or posteromedially, and the submandibular gland anteriorly.
Etichette: ACR, Head - Neck, Malformations
mercoledì 19 ottobre 2005
There is a hyperdense cyst at the roof of the third ventricle at the foramen of Monro (Figure 1, Figure 2, Figure 3 andFigure 4). There is no enhancement of the cyst. The ventricles are nondilated.
Diagnosis: Colloid cyst
Colloid cysts are rare cystic lesions that are classically located at the anterior roof of the third ventricle at the foramen of Monro. They can be pedunculated, which can make the cyst mobile and lead to sudden ventricular obstruction at the foramen of Monro. Patients are typically in their third to fourth decade of life and present with intermittent or persistent headaches due to the increased intracranial pressure from obstruction of CSF outflow. Colloid cysts are treated microsurgically, endoscopically, or with biventricular shunts in nonsurgical candidates. These are surgical emergencies in cases of acute hydrocephalus.
Colloid cysts are typically hyperdense on noncontrast CT and typically do not demonstrate any enhancement. Case reports have documented rare cyst wall enhancement. Their MR characteristics are variable due to the variations in protein, mucin, and water content of the cyst fluid. Calcifications and hemorrhage are rare.
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