mercoledì 23 novembre 2005

Gradenigo syndrome


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.

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

Tuberous sclerosis


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
- lymphangioleiomyomatosis
- retinal hamartoma
- macules

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.