Search PubMed⌕ Search

Biomedical subjects

A J Kumar

Publications and source records attributed to A J Kumar.

At least 73 records · Page 4Linked to original sources
PubMed1978

Traumatic vertebrobasilar occlusive disease in childhood.

Vigorous gymnastics and repeated manipulations of the cervical spine by a chiropractor were associated with headaches and transient cranial nerve deficits in a 7-year-old boy who had a history of birth trauma. Progressive cerebellar dysfunction was later accompanied by a visual field defect. A computerized axial tomography scan revealed a cerebellar infarction, and arteriograms showed vertebral and basilar occlusions. Passive stretching of the cervical spine during chiropractic maneuvers may lead to vertebral artery thrombosis with subsequent embolization into the basilar artery circulation.

Athletic Injuries↗
PubMed1976

An angiographic study of the carotid arterial and jugular venous systems in the cat.

Standard techniques for performing carotid angiography in dogs and in man were adapted to the cat in order to study the vascularization of both intracranial and extracranial structures. Venous drainage was examined by venography of selected vessels. The carotid-cerebral and the vertebral-basilar arterial systems of the cat were studied, although no attempt was made to define the territory supplied by each system. In serial angiograms, vascularization of the rete mirabile conjugatum was visualized and distinct arterial and venous retia were delineated. Large facial veins were seen approximately one second after the intra-arterial injection of radio-contrast material. The early filling of the large facial veins appeared to be the result of an artery-to-venous shunt. Contrast material flowed posteriorly in these veins and drained into the venous rete. When contrast material was injected either into the sagittal sinus or retrograde in the external jugular vein, the internal jugular vein was visible in four of ten cats. This vessel drained blood directly from intracranial contents before anastomosis with the vertebral and external jugular veins.

Animals↗
PubMed1975

Changes in regional blood-flow and water content of brain and spinal cord in acute and chronic experimental hydrocephalus.

The effects of kaolin-induced hydrocephalus on regional blood-flow and water content of cat brain and spinal cord were measured. The role of the central canal of the spinal cord as an alternative pathway for cerebrospinal fluid in experimental hydrocephalus was also studied by positive contrast ventriculography. In comparison with normal cats, blood-flow in the cerebrum, cerebellum and brain stem of cats with acute hydrocephalus was reduced by more than 20 per cent: in those with chronic hydrocephalus it was reduced by only 12 per cent. There was an absolute increase of 1-5 per cent in water content of the brain in cats with acute hydrocephalus. Water content in the spinal cord was increased by 6 per cent in cats with acute hydrocephalus and by 8 per cent in those with chronic hydrocephalus. When the increased water-content was taken into account, hydrocephalus caused no significant change in blood-flow in the cervical, thoracic or lumbar spinal cord. Contrast material perfused through the ventricles of hydrocephalic cats flowed directly into the enlarged central canal of the spinal cord. Kaolin-induced arachnoiditis completely obstructed communication between the ventricles and the cranial subarachnoid space. The contrast material in the central canal communicated both with the cavities extending into the dorsal columns and with the spinal subarachnoid space. When kaolin was injected directly into the spinal subarachnoid space there was an increase in spinal water-content, without an enlarged central canal. These results suggest that in addition to kaolin-induced arachnoiditis, increased intraluminal pressure is necessary to enlarge the central canal.

Acute Disease↗
PubMedDate not supplied

Imaging and clinical spectrum of rhabdomyosarcoma in children.

We retrospectively analyzed the MRI findings of rhabdomyosarcoma (RMSA) in 23 patients to evaluate its role in staging and management. Heterogeneous signal abnormalities were noted in the sarcoma lesions with significant contrast enhancement. Seven head and neck cases showed direct bone invasion and destruction; only one had distant bony metastasis. Metastasis was noted in the lymph nodes, lung, bone, abdominoperitoneum, and head and neck soft tissue. MRI findings of RMSA are most helpful in staging and assessing therapeutic response.

Child↗
PubMedDate not supplied

A second look at unenhanced spinal magnetic resonance imaging of malignant leptomeningeal disease.

The purpose of this study is to evaluate the use of unenhanced magnetic resonance (MR) imaging in identifying malignant leptomeningeal disease (MLD). Included in this study were fifty patients with evidence of leptomeningeal enhancement on post-gadolinium MR images and with cytological confirmation of MLD. Unenhanced, T1-weighted spin-echo (SE) MR images of the spine were analyzed for loss of cerebrospinal fluid (CSF) clarity, poor definition of the conus medullaris, thickened and clumped nerve roots, and nodules. Patterns of leptomeningeal enhancement on post-gadolinium, T1-weighted SE images were noted. Findings of MLD on unenhanced MR images were observed in 41 (85%) of 48 studies of the lumbar spine, 10 (50%) of 20 studies of the thoracic spine, and two (33%) of six studies of the cervical spine. In the lumbar spine, thickened and clumped nerve roots, poor definition of the conus medullaris, loss of CSF clarity, and nodules were observed with decreasing frequency. The signs of MLD on unenhanced images of the cervicothoracic spine included nodules and clouding of CSF. Patterns of leptomeningeal enhancement included linear, linear/nodular, nodular, enhancement of nerve roots, and stacking, with tumor filling the lumbosacral canal. Findings of MLD were present on 73% of the unenhanced MR images of the spine. Recognition of MLD on unenhanced MR images can guide the appropriate work-up and therapeutic approach.

Adult↗
PubMedDate not supplied

Positive contrast ventriculography in cats with experimental obstructive hydrocephalus.

Cerebrospinal fluid pathways were studied in both normal and experimental obstructed hydrocephalic cats by positive contrast ventriculography. Either water soluble or insoluble contrast material was injected into the lateral cerebral ventricles, and radiographs were taken of the head and spinal cord. In the normal cat, the contrast material freely flowed throughout the spinal fluid spaces. The contrast material accumulated in the cisterna magna, and from there extended into the cranial and spinal subarachnoid spaces. In the kaolin-induced hydrocephalic cat, the outlets from the fourth ventricle were obstructed, and direct communication between the ventricular system and the subarachnoid spaces no longer existed. In these cats, the contrast material passed directly down the central canal of spinal cord and its movement was followed throughout the entire length of the canal. At the lower lumbar-sacral regions, the material perforated the cord and flowed into the subarachnoid space. At all levels, the central canal was enlarged and local dilatations were seen extending dorsally.

Animals↗
PubMedDate not supplied

CT myelography and MR imaging of acute transverse myelitis.

Two patients with acute transverse myelitis were evaluated by both CT myelography and magnetic resonance. Computed tomographic myelography showed fusiform cord enlargement involving several levels; one patient had a subtotal block in the thoracic spine. Magnetic resonance displayed similar findings of cord enlargement. The demonstration of cord swelling in acute transverse myelitis is an uncommon radiologic manifestation of the disease.

Acute Disease↗
PubMedDate not supplied

MR imaging of normal nasal cycle: comparison with sinus pathology.

Sequential MR examinations of the nasal cavity and paranasal sinuses were performed within a 6-8 h period in five normal volunteers. The nasal mucosal volume and signal intensities (T2 weighted) were shown to alternate from one side to the other during this period. When a topical vasoconstrictor was applied, this cycle was interrupted. These cyclical changes were limited to the mucosa of the turbinates, nasal cavity, and ethmoid sinus, representative of the nasal cycle. The maxillary, frontal, and sphenoid sinuses were not affected. The hyperintensity of the nasal cycle on T2-weighted images was similar to that shown by inflammatory mucosa. Squamous cell carcinoma within the nasal cavity and paranasal sinuses has characteristically demonstrated a lower signal intensity on T2-weighted images. Awareness of these cyclical nasal and paranasal appearances reduces the likelihood of inflammatory disease being confused with normal physiologic changes within the nasal area.

Adult↗
PubMedDate not supplied

Intradural spinal metastases in pediatric patients with primary intracranial neoplasms: Gd-DTPA enhanced MR vs CT myelography.

Recently, the application of intravenous gadolinium-diethylenetriamine pentaacetic acid (Gd-DTPA) has been shown to improve the detection of intradural extramedullary spinal disease in adults. The ability of Gd-DTPA enhanced magnetic resonance (MR) to detect intradural extramedullary spinal metastases was studied in pediatric brain tumor patients. Spinal MR images before and after intravenous injection of Gd-DTPA were analyzed retrospectively in eight pediatric patients with known intracranial neoplasms and clinically suspected subarachnoid tumor seedings. Contrast enhanced spinal MR was compared with CT myelography in four of these patients. In our pediatric population Gd-DTPA enhanced images revealed tumor seeding not appreciable on noncontrast images. Although CT myelography has been the accepted standard investigation in the evaluation of suspected spinal metastases in children, we found that contrast enhanced MR is equal or superior in sensitivity to CT myelography. Spinal MR also provided information not obtainable via CT myelography. In the future, Gd-DTPA enhanced spinal MR should be considered in the initial evaluation of suspected subarachnoid spinal metastases in pediatric patients with known primary brain tumors.

Adolescent↗
PubMedDate not supplied

Pitfalls and artifacts encountered in clinical MR imaging of the spine.

Magnetic resonance (MR) imaging of the spine has become widely accepted as a valuable diagnostic tool. However, there are a number of artifacts and pitfalls associated with spinal MR imaging. Chemical shift artifacts may be induced by bone marrow, epidural fat, or intradural fat. Motion artifacts arise from several sources, which include respiration, flow of fluids, and swallowing. Artifacts due to a nonuniform magnetic field are particularly noticeable within trabecular bone or at bone-soft tissue interfaces but may also be caused by incomplete fat saturation or the presence of metal near the spine. Protocol errors may cause artifacts such as saturation, phase wraparound, truncation, radio-frequency interference, shading, and partial volume averaging. Use of fat saturation, use of motion and flow compensation, and careful screening of patients for metal in clothing can help reduce the occurrence of artifacts. In addition, use of an optimal imaging technique is essential and should include use of the proper surface coil, field of view, and pulse sequence.

Artifacts↗
PubMedDate not supplied

Clinical-angiographic correlation of ophthalmodynamometry in patients with suspected carotid artery disease: a prospective study.

A prospective, clinical study was performed on patients with suspected carotid artery disease to compare the accuracy of compression and suction ophthalmodynamometry with carotid artery stenosis as determined by arteriography. Results were analyzed with respect to current criteria for classification and determination of "significant" carotid artery disease. Although our results suggest that the best correlation for both procedures with arteriography is a ratio of the corrected intraocular pressure to the systolic brachial blood pressure, these results were not statistically improved over those obtained using uncorrected systolic or diastolic values. Both suction and compression ophthalmodynamometry are equally accurate with levels approaching 80 percent; however, neither test is sensitive enough to be used alone as a screening technique. Arteriography remains the best procedure for the determination of carotid artery disease.

Carotid Arteries↗
PubMedDate not supplied

AIDS-related CNS cryptococcosis: radiologic-pathologic correlation.

PURPOSE: This study evaluates the effectiveness of cranial CT and MR in detecting autopsy findings of AIDS-related CNS cryptococcosis. METHODS: Final imaging studies compared with pathology were CT in eight patients (five with contrast) and MR in five patients (all with Gd-DTPA). RESULTS: Neither modality effectively identified cryptococcal meningitis. Punctate hyperintensities were seen in all patients with MR and corresponded pathologically to both perivascular spaces dilated by cryptococcal infection and cryptococcomas. Pathologically, cryptococcomas were more common than dilated perivascular spaces. MR detected more cryptococcomas than did CT, but both modalities underestimated the number of lesions seen at autopsy. Contrast enhancement of cryptococcomas and cryptococcal meningitis was uncommon. CONCLUSIONS: CNS cryptococcosis was more effectively demonstrated by MR than by CT, but both modalities underestimated the pathologic extent of the disease. Cryptococcal lesion contrast enhancement was unusual possibly because of the immunocompromised state of our patients and the unique characteristics of the organism itself.

Acquired Immunodeficiency Syndrome↗
PubMedDate not supplied

Brain atrophy in 18 patients with Down syndrome: a CT study.

Individuals with Down syndrome develop neuropathologic and in some cases clinical evidence of Alzheimer disease after age 40. We compared CT scans of 18 Down syndrome subjects, 26-70 years old (seven of whom satisfied criteria for dementia), with 175 screened normal volunteer control subjects for evidence of cortical and subcortical atrophy. CT scans were analyzed as a function of age and cognitive status. The suprasellar cistern ratio, presumed to measure mesial temporal-lobe atrophy (or hypoplasia), was correlated with severity of cognitive impairment, even when age effects were removed. The suprasellar cistern ratio predicted dementia status with an accuracy of greater than 75%. Brain measurements on CT scans showed a distinct pattern of increased abnormality with age in patients with Down syndrome; this differed clearly from that seen in controls.

Adult↗
PubMedDate not supplied

Unruptured intracranial arteriovenous malformations do cause mass effect.

Sixty patients with clinically unruptured intracranial arteriovenous malformations were studied with high-resolution computed tomography. In 33, local and distant mass effects were evidenced by compression, distortion, and displacement of normal anatomic structures by the malformation, its afferent and efferent vessels, and the surrounding edema.

Brain Edema↗