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Biomedical subjects

M E Mawad

Publications and source records attributed to M E Mawad.

30 records · Page 2Linked to original sources
PubMed1983

Computed tomography of the nasopharynx and related spaces. Part I: Anatomy.

The normal computed tomographic anatomy of the nasopharynx and pterygopalatine and infratemporal fossae is analyzed. Particular attention is given to the distinction between deglutitional and masticatory muscles. The relations of the palatal muscles to the eustachian tube are described in detail. Those soft-tissue features that, when they deviate from normal, can provide early detection of nasopharyngeal lesions are emphasized.

Humans↗
PubMed1983

Computed tomography of the brain stem with intrathecal metrizamide. Part I: the normal brain stem.

In summary, the anatomic details of the brain stem are exquisitely demonstrated with metrizamide CT. The obex is the zone of transition from the closed medulla, which has a conical pear-shaped appearance to the quadriconcave open medulla. The pyramids and inferior olivary nuclei characterize the anterior surface of the open medulla, whereas the median sulcus and the cranial nerve nuclei constitute the floor of the fourth ventricle at the same level. The mushroomlike appearance of the pontomedullary junction is easily reproducible with the restiform bodies forming the posteriorly diverging biped. The seventh and eighth nerves are usually seen at this level or on the adjacent higher section of the low pons. The brachia pontis are well delineated in almost their entire length at the level of the low pons as they bound the fourth ventricle laterally. The trigeminal nerves are seen at the level of the midpons, which is a few millimeters lower than the isthmus. The latter constitutes the junction of the pons with the mesencephalon. The colliculi divide the midbrain into two levels of axial cross section: the inferior collicular level, which may or may not show the trochlear nerve, and the superior collicular level, which features anteriorly the suprasellar cistern and its contents. Air is an inadequate contrast agent for CT for the demonstration of the surface features of the brain stem because of partial filling of the cisterns and meniscus formation that precludes a detailed outline. Metrizamide, however, with careful technique, fills the fourth ventricle and subarachnoid space both infra- and supratentorially. High-resolution scanning using primary reconstruction, and thin tomographic sections of no more than 5 mm are a necessity for metrizamide CT. Consecutive scans should not be spaced more than 5 mm apart if all the features of the brain stem are to be evaluated. The demonstration of the various grooves and protuberances on the surface of the brain stem provides a unique opportunity for evaluating focal atrophy and focal swelling henceforth impossible to visualize consistently.

Brain Stem↗
PubMed1983

Computed tomography of the brain stem with intrathecal metrizamide. Part II: lesions in and around the brain stem.

The practical usefulness of computed tomography with intrathecal metrizamide in imaging the brain stem is illustrated in six examples where the lesions were misdiagnosed on intravenously enhanced computed tomography, angiography, or air study. Focal and diffuse atrophic changes of the brain stem were demonstrated in symptomatic patients where none of the other radiographic or clinical investigations were conclusive. Metrizamide computed tomography is probably the most sensitive method for imaging lesions in and around the brain stem and cerebellopontine angle.

Adolescent↗
PubMed1982

Computed tomography of cerebellar hemangioblastomas.

Ten patients with proven cerebellar hemangioblastomas were studied by computed tomography (CT). Angiography was obtained in seven cases. Eight patients had a cyst and a nodule, one presented with a nodule only, and one with a cyst only. Some morphological features on CT were found particularly helpful in establishing the histological diagnosis of this tumor. All cysts in this series had either a nonenhancing wall or a thin, discontinuous enhancement rim. The remarkable thinness of the cyst is a helpful feature in differentiating between hemangioblastomas and ring enhancement due to metastases. All hemangioblastoma nodules are near the pia, particularly the tentorial surface or the occipital surface of the cerebellum. The nodules in this series were isodense with brain before and enhanced significantly after contrast medium injection, matching or exceeding the density of the straight sinus. In three cases, a large vessel leading to the nodule could be identified on CT. In only one of 10 cases was there a central lucency in the enhancing nodule. The CT density of the hemangioblastoma cyst correlated with the size of the nodule, i.e., the larger the nodule, the denser the cyst on precontrast studies. Compared to cerebellar astrocytomas, hemangioblastomas are not calcified and tend to have relatively small nodule associated with a large cyst. For a given size cyst, the nodule in an astrocytoma is usually larger.

Adult↗
PubMedDate not supplied

Spinal cord ischemia after resection of thoracoabdominal aortic aneurysms: MR findings in 24 patients.

MR images of the thoracic spinal cord were made in 24 patients who developed signs and symptoms of spinal cord ischemia or infarction following surgery for a thoracoabdominal aortic aneurysm. Findings consisted primarily of four different patterns of signal abnormalities in the distribution of the anterior spinal artery. These abnormalities were identified as types A-D, depending on the degree of involvement of the gray matter and surrounding white matter. We found good correlation between the distribution of the signal abnormalities in the cord, the severity of the neurologic deficits, and the clinical outcome. MR is the imaging method of choice for diagnosing spinal cord ischemia or infarction. A thorough knowledge of the spinal cord arterial territories is crucial for characterizing ischemic MR signal abnormalities and for differentiating them from other causes of myelopathy.

Adolescent↗
PubMedDate not supplied

Computed tomography of primitive neuroectodermal tumors.

The primitive neuroectodermal tumor is a neoplasm of young individuals that occurs predominantly in the supratentorial compartment. It appears on computed tomography as a bulky mass, often with calcification with predominantly homogeneous enhancement but on occasion with cystic or necrotic areas. Cerebrospinal fluid seeding was observed in more than half the cases in our series. The patients had a short survival period (7-24 months). Despite surgery, radiation, and chemotherapy, further growth of this tumor has not been prevented.

Adolescent↗
PubMedDate not supplied

In vivo NMR imaging of tissue sodium in the intact cat before and after acute cerebral stroke.

The first in vivo nuclear magnetic resonance (NMR) images of tissue sodium in the intact animal are presented. The distribution of sodium in the normal cat's head is described. An experimental stroke was surgically induced. Sodium NMR imaging showed a pronounced focal increase in cerebral sodium concentration 9 hr after ligation of the middle cerebral artery. The method appears to be very sensitive for early detection of infarction. The measured increase in the regional sodium NMR signal probably reflects both a true increase in concentration of brain sodium and an increased NMR visibility of the sodium nucleus in the region of the infarction.

Animals↗
PubMedDate not supplied

Computed tomography of the anteverted internal auditory canal.

A symmetric variation in the course of the internal auditory canals, visualized best on axial computed tomographic views with thin sections, was observed in three of 75 patients examined mainly for hearing, vestibular, and facial nerve dysfunction. The incidence may be lower in an unselected population. In coronal section, with either pluridirectional or computed tomography, an anteverted internal auditory canal may mimic the normal configuration of "medial narrowing" because of the effect of partial sectioning of an angled cylinder with a thin beam. The pathologic significance of this finding is uncertain. In the three cases reported, it was associated with adult-onset uni- or bilateral hearing loss. Vestibular function may be compromised but may not be symptomatic. Facial nerve function was not impaired.

Adult↗
PubMedDate not supplied

Patterns of spinal cord atrophy by metrizamide CT.

Forty patients with cervical myelopathy underwent high-resolution computed tomography (CT) with intrathecal administration of metrizamide for evaluation of cervical spinal cord atrophy. Thirty of them showed evidence of either focal atrophic distortion or generalized accentuation of the anatomic surface features of the spinal cord. Patients with a Chiari malformation or syringomyelia were excluded. The characteristic features in cervical spondylosis and canal deformity include flattening of the ventral surface of the cord, central infolding, beaking of the lateral funiculi, and wasting of the dorsal surface of the cord. Patients with motor neuron disease showed a combination of anterolateral and posterolateral atrophy reflecting underlying degeneration of the anterior horn cells and/or corticospinal tracts, respectively. Those with monomelic motor neuron disease had a striking ipsilateral hemiatrophy of the spinal cord. Among those presenting with spastic paraparesis, seven with clinically definite multiple sclerosis showed diffuse atrophy or focal degeneration due to a localized plaque of demyelination. Two cases of cord neoplasm showed atrophy secondary to ascending or descending degeneration of the long tracts.

Atrophy↗
PubMedDate not supplied

Computed tomography of the cervical lymph nodes: use of intravenous contrast enhancement.

Intravenous contrast administration increases the sensitivity of computed tomographic scanning for enlarged cervical lymph nodes but requires a detailed knowledge of neck anatomy, especially in order to distinguish certain normal vessels from involved nodal groups. Along the collar chain, relations between the parotid and submandibular salivary glands and the posterior and anterior facial veins and facial artery are analyzed. The digastric muscle is defined as a transitional landmark between collar and deep cervical nodes. Along the deep cervical chain, emphasis is on the internal jugular vein, its variability in size, and its relations to the anterior scalene and omohyoid muscles.

Humans↗
PubMedDate not supplied

MR appearance of an orbital leiomyoma.

The authors describe the MR appearance of an intraconal orbital vascular leiomyoma that probably arose from smooth muscle in the wall of a vein. Cavernous hemangiomas, schwannomas, neurofibromas, and other well-encapsulated masses can have a similar appearance.

Aged↗