Differential diagnosis of cerebral hemispheric pathology: multimodal approach.

This article gives a comprehensive review and illustrations of the imaging features of various pathological conditions and clinical syndromes associated with cerebral hemispheric involvement. The various conditions are described and defined to provide a basis for the differential diagnostics. The hypotheses relating to the pathology of the various syndromes are discussed with special emphasis on excitotoxic mechanisms for explaining the subsequent cerebral hemiatrophy.

The "thickened" ligamentum flavum: is it buckling or enlargement?

BACKGROUND AND PURPOSE: Thickening of the LF is ascribed to buckling due to DSN. Uncertainty exists as to whether this can occur without DSN. Our primary hypothesis was that facet degenerative changes alone, independent of DSN, can thicken the LF. Our secondary hypothesis was that inflammatory changes surrounding degenerative facet joints may incite thickening. MATERIALS AND METHODS: Fifty-two patients were divided into 1 of 3 groups: group 1 (normal lumbar spine, n = 21), group 2 (LF thickening and FH with normal height of the L4-5 disk, n = 18), and group 3 (LF thickening and FH with decreased height of the L4-5 disk, n = 13). LF thickness measured on axial T1WI at the midpoint of the LF length was compared with that in group 1. Facet joints were evaluated for spurring, joint fluid, and cortical irregularity, indicating facet degeneration. Enhancement of the facet joints and LF thickening were also evaluated (n = 2). The Student t test was used to compare groups. RESULTS: Normal LF thickness (group 1) was 3.1 mm, whereas LF thickness averaged 4.9 mm in group 2 and 5.3 mm in group 3 (both P < .001). Patients with asymmetric LF thickness showed greater LF thickness on the side with greater FH. There was more LF enhancement on the side with greater facet degenerative disease. CONCLUSIONS: LF thickening can be secondary to facet degenerative changes, independent of DSN. Inflammatory changes may be an inciting factor for LF thickening.

The rare third branchial cleft cyst.

Third branchial cleft cysts (BCCs) are rare entities that represent abnormal persistence of the branchial apparatus. On CT examination, these cysts appear as homogeneous low-attenuation masses with well-circumscribed margins; on MR imaging, they demonstrate variable signal intensity on T1-weighted images and are hyperintense relative to muscle on T2-weighted images. Definitive treatment is surgical excision. We present a case of a third BCC and describe its diagnosis and treatment.

Lateral pterygoid muscle rhabdomyolysis.

We report a case of rhabdomyolysis due to acetaminophen overdose involving the lateral pterygoid muscles bilaterally, in addition to the other muscles of the abdomen and pelvis. To the best of our knowledge, involvement of the head and neck muscles by rhabdomyolysis has not been reported previously. The isolated involvement of the lateral pterygoid muscles may be due to the presence of the surrounding pterygoid venous plexus. It is important to be aware of the imaging characteristics of rhabdomyolysis and to consider the possibility of involvement of head and neck muscles to aid in early diagnosis and avoid misinterpretation of the imaging findings.

MR imaging of the craniovertebral junction.

The rapid growth of MR imaging has brought a renewed interest in the craniovertebral junction. Many congenital and acquired lesions affect this region and compress the underlying cervicomedullary junction and cranial nerves. Basilar invagination, basilar impression, and cranial settling are readily assessed with MR imaging in the sagittal plane, and evaluation of this region on all cranial and cervical spine studies should become routine.

Screening CT of the brain determined by CD4 count in HIV-positive patients presenting with headache.

BACKGROUND AND PURPOSE: Few studies have examined HIV-positive patients presenting with uncomplicated headache for clinical variables that might be predictive of those patients who would most benefit from CT. Because of the value of CD4 counts in predicting the relative risk of developing opportunistic infections and neoplasms, we assessed the diagnostic yield of screening CT in HIV-positive patients presenting with headache as sorted by CD4 count. METHODS: We reviewed CT scan results and CD4 counts in patients presenting with headache uncomplicated by altered mental status, meningeal signs, neurologic findings, or symptoms of subarachnoid hemorrhage. For analysis, scans were considered positive or negative and were grouped according to CD4 counts of less than 200 cells/microL, 200 to 499 cells/microL, and equal to or greater than 500 cells/microL. The results were then analyzed using the chi2 test. RESULTS: One hundred seventy-eight HIV-positive patients underwent a total of 204 unenhanced and contrast-enhanced CT examinations. One hundred twenty-eight (62.7%) of the scans were negative, and 76 (37.3%) were positive. Of the positive scans, 58 (76.3%) showed atrophy only and 18 (23.7%) showed mass lesions or white matter lesions. All cases that were positive for mass lesions or white matter lesions occurred in patients with CD4 counts less than 200 cells/microL (P = .04). CONCLUSION: A recent CD4 count provides an important predictor variable when considering performing CT in HIV-positive patients presenting with uncomplicated headache. Performing CT of the head for patients with CD4 counts equal to or greater than 200 cells/microL is of questionable value considering the low prevalence of positive CT findings. For this select group of patients, MR imaging may be more appropriate than CT. Patients with CD4 counts less than 200 cells/microL should undergo CT because of the high prevalence of positive scans.

Anatomy of the cranial nerves.

The anatomy of cranial nerves I and III through XII are presented. Each nerve is diagrammatically illustrated from its nuclear or its sensory origin and correlated with magnetic resonance and computed tomography images. The important identifying anatomical landmarks are demonstrated along the course of each nerve. Peripheral motor and sensory components are also discussed.

MR appearance of trigeminal and hypoglossal motor denervation.

PURPOSE: To illustrate and describe the appearance of both long-standing and relatively recently occurring motor denervation of the hypoglossal nerve and of the third (mandibular) division of the trigeminal nerve (V3), with emphasis on findings particular to MR imaging. METHODS: Findings from 11 patients with V3 denervation and from seven patients with hypoglossal denervation resulting from a variety of abnormalities were reviewed retrospectively. The motor denervation appearance and functional compromise of the affected musculature are described in terms of the chronicity of the denervation process. RESULTS: The appearance of V3 and hypoglossal motor denervation varies with the chronicity of the process. Long-standing denervation results in extensive fatty replacement and a decrease in the size of the affected musculature. Relatively recently occurring denervation results in abnormal contrast enhancement and edemalike signal changes in the denervated musculature. Fatty replacement was observed acutely in hypoglossal denervation but did not manifest until the subacute stage in V3 denervation. Increased volume of the denervated musculature may also accompany acute denervation signal changes. CONCLUSION: V3 and hypoglossal denervation have a variable appearance depending on the chronicity of the process. Recognition of MR imaging patterns of denervation may allow earlier diagnosis of a denervating lesion and may help to distinguish denervation from similar-appearing processes, such as infection or neoplasia.

Atypical skull base paragangliomas.

We present two cases of unusually large skull base paragangliomas. The first tumor was accompanied by marked bony destruction of the central skull base and multiple associated cysts. The second tumor arose along the petrous ridge, with a large intracranial component. The CT, MR imaging, angiographic, histologic, and electron microscopic findings of these unusual lesions are described.

Cortical and subcortical T2 shortening in multiple sclerosis.

Low signal intensity on long-repetition-time MR sequences has been observed in deep gray matter structures in patients with multiple sclerosis. This T2 shortening most likely represents a nonspecific degenerative process. We recently observed T2 shortening in the pericentral cortical gray matter and subcortical white matter in a patient with severe multiple sclerosis and we postulate that this represents an additional manifestation of neural degeneration.

Nonatheromatous carotid artery disease.

Common and uncommon nonatheromatous diseases affecting the cervical carotid artery are discussed. Specifically, the radiographic and pertinent clinical features of cervical carotid artery congenital variants, dissection, fibromuscular dysplasia, Takayasu's arteritis, and infection are described. Catheter angiography continues to have an important role in the diagnosis of many of these conditions. Magnetic resonance imaging techniques are emerging as a useful adjunct to catheter angiography and occasionally may be the primary imaging modality for diagnosis.

The forgotten condyle: the appearance, morphology, and classification of occipital condyle fractures.

PURPOSE: To evaluate the appearance, morphology, and treatment of occipital condyle fractures (OCF). METHODS: Cases were collected by a retrospective and prospective analysis of teaching files and case logs. Patients' charts, when available, were reviewed for age, sex, mode of injury, physical examination, Glascow Coma Scale score, and associated injuries. Plain films and CT images were reviewed to determine OCF type and to assess for the presence of associated cervical spine and/or intracranial trauma. RESULTS: Fifteen patients with OCF, 13 occurring in a 43-month period, were identified. Ten patients were involved in motor vehicle accidents. Severity of closed head injury and associated clinical findings were variable. Three patients had associated cervical spine fracture. According to the Anderson and Montesano classification, two patients (13%) had type I OCF, eight patients (54%) had type II OCF, and five (33%) had type III OCF. Fourteen of the fractures were identified on screening trauma head CT scans. Treatment varied according to the presence of associated injuries and stability of the cervical spine. CONCLUSIONS: Although OCFs are rare, they will be encountered by most radiologists who see a significant amount of trauma. Type II OCFs were the most common fracture type in our series. Type III fractures were the second most common and potentially unstable. CT should be initiated at the level of the C-1 ring to screen for the presence of OCF in all patients who have suffered trauma.

Oral cavity: anatomy and pathology.

The oral cavity and oropharynx comprise the upper portion of the aerodigestive tract. These two regions are distinguished from each other because pathologic processes differ in their presentations, prognoses, and histologic grades. The normal anatomy of the oral cavity, vestibule, and oral cavity proper is discussed and is followed by a discussion of the sublingual and submandibular spaces. The diversity of pathologic processes that occur in these regions is then presented as well as the more common pitfalls.

Congenital anomalies of the cervical spine.

A wide variety of congenital pathology affects the cervical spine and underlying spinal cord. This article discusses commonly encountered conditions under the categories of osseous anomalies, Chiari malformations, dysraphic conditions, and skeletal dysplasias. Osseous anomalies tend to involve the upper cervical spine to a greater degree than the lower cervical spine. Chiari malformations warrant inclusion on the basis that they have many manifestations within the cervical spine. Dysraphic conditions resulting from failure of either primary or secondary neurulation are distinctly uncommon in the cervical spine compared with the lumbar spine and are, therefore, only briefly discussed. Skeletal dysplasias encompass a diverse group of uncommon entities but may produce significant radiographic abnormalities and may be associated with clinical symptomatology.

Hemorrhagic intracranial parenchymal metastases from primary retroperitoneal neuroblastoma.

An unusual case of parenchymal hemorrhagic metastases to the cerebrum and cerebellum in a child with retroperitoneal neuroblastoma is presented. While isolated parenchymal central nervous system (CNS) metastases have not typically been considered in association with neuroblastoma, review of the literature suggests an increased frequency of this manifestation, especially since 1980. Metastatic neuroblastoma should be included in the differential diagnosis of multiple hemorrhagic parenchymal brain lesions in the pediatric population.

MR angiography artifact due to metal joint of ventriculoperitoneal shunt mimicking severe carotid stenosis.

An artifact due to the metal joint of a ventriculoperitoneal shunt resulted in a diagnosis of severe internal carotid artery stenosis at magnetic resonance angiography. Conventional x-ray angiography showed the presence of the metal joint and revealed that the artery was not stenotic.

Musculoskeletal causes of spinal axis compromise: beyond the usual suspects.

The majority of cases of spinal canal compromise are caused by common pathologic conditions, including degenerative spondylosis, infection, trauma, and metastatic disease. However, there are other causes of spinal canal compromise that, though unusual, may be seen in everyday practice. Congenital abnormalities of the spine that may produce spinal canal compromise include the os odontoideum, hemivertebra, diastematomyelia, and achondroplasia. Arthritides and enthesopathies such as rheumatoid arthritis, ankylosing spondylitis, synovial cysts of the facet joint, calcium pyrophosphate dihydrate deposition or hydroxyapatite deposition, and ossification of the posterior longitudinal ligament or ligamentum flavum may lead to narrowing of the spinal canal. Primary spinal tumors and tumorlike lesions such as hemangioma, aneurysmal bone cysts, osteochondroma, and osteoblastoma may also cause spinal canal stenosis. Finally, Paget disease of bone may compromise the spinal cord. Radiologists should be aware of these unusual musculoskeletal causes of spinal canal compromise and their radiologic and clinical features.

Hypoglossal nerve palsy: a segmental approach.

Hypoglossal nerve (cranial nerve XII) palsy is uncommon. Damage to this nerve produces characteristic clinical manifestations, of which unilateral atrophy of the tongue musculature is the most important. When these features are recognized, the radiologist, armed with knowledge of the normal anatomy of the area, can focus on each segment of the nerve in search of a cause. The hypoglossal nerve is divided into five segments: the medullary, cisternal, skull base, nasopharyngeal/oropharyngeal carotid space, and sublingual segments. Because each segment is usually affected by different disorders, localizing a lesion to a particular segment allows the radiologist to narrow the differential diagnosis. In this way, the most efficient imaging strategy for evaluation of the symptoms can be developed. Both computed tomography and magnetic resonance imaging are useful in assessing dysfunction of the hypoglossal nerve; the choice depends on the status of the patient and the preference of the radiologist.