R. Nuri Sener

MR of craniocerebral hemiatrophy

The magnetic resonance (MR) findings of three patients with cerebral hemiatrophy, the so-called Dyke-Davidoff-Masson syndrome, which is characterized by variable degrees of unilateral loss of cerebral volume and compensatory changes of the calvarium are presented. The condition was due to middle cerebral artery stroke in all patients. The pathologic alterations of cerebral tissue and the brainstem were reflected in detail on the MR studies. MR findings in addition to the primary vascular insult included prominence of the cortical sulci and perimesencephalic cistern in one subject with acquired infarction, but an absence of such generalized sulcal prominence in two cases of congenital infantile paralysis. Otherwise the secondary ipsilateral pathologic observations were quite similar in the patients with congenital and acquired ischemic disease and encompassed a unilaterally small cerebral hemisphere together with ipsilateral diploic calvarial expansion, elevation of the petrous bone and orbital roof, and hypoplasia/atrophy of the cerebral peduncle. Although computed tomography (CT) and MR are complimentary, it is felt that MR represents the imaging procedure of choice with respect to the assessment of the etiology and extent of cerebral parenchymal involvement in patients presenting with a clinical combination of congenital or early onset of seizures, hemiparesis/plegia, and/or craniofacial asymmetry.

L-2 hydroxyglutaric aciduria: proton magnetic resonance spectroscopy and diffusion magnetic resonance imaging findings.

A 10-month-old boy was reported with the diagnosis of L-2 hydroxyglutaric aciduria. Amino acid chromatographic analysis revealed an 80-fold increase of hydroxyglutaric acid in the urine. Proton magnetic resonance (MR) spectroscopy of the brain obtained with the hybrid chemical shift imaging sequence (repetition time = 1,500 milliseconds, echo time = 40 milliseconds) revealed prominent peaks resonating at 2.50 ppm, which were attributable to L-2 hydroxyglutaric acid. Diffusion MR imaging was obtained using the echo-planar trace sequence (repetition time = 5,700 milliseconds, echo time = 139 milliseconds). Two different diffusion patterns were evident: a restricted diffusion pattern in the globi pallidi and an increased diffusion pattern in the white matter.

Nonketotic hyperglycinemia: Diffusion magnetic resonance imaging findings

We report about a boy with nonketotic hyperglycinemia who was studied at 15 days of life with a follow-up examination at age 6 months. Magnetic resonance (MR) imaging revealed progressive atrophy, callosal thinning, and delayed myelination. Glycine peaks were shown by proton MR spectroscopy at 3.56 ppm with a long echo time (TE, 135 milliseconds; TR, 1500 milliseconds). Echo-planar diffusion MR imaging (TR, 5700 milliseconds; TE, 139 milliseconds) at 15 days of life revealed high-signal lesions in the pyramidal tracts, middle cerebellar pedicles, and dentate nuclei on b = 1000 s/mm2 images associated with low apparent diffusion coefficient (ADC) values. By age 6 months, the lesions became more prominent on b = 1000 s/mm2 images with lower ADC values. Diffusion MR imaging findings likely reflected the histopathologic changes of the disease which consisted of spongiosis of the myelinated brain tissue due to myelin vacuolation.

Canavan disease: Diffusion magnetic resonance imaging findings

A 15-month-old boy with Canavan disease is reported in whom a restricted diffusion pattern on diffusion magnetic resonance imaging (MRI) (high signal on b = 1,000 mm2/s images and low apparent diffusion coefficient [ADC] values) was evident in the affected regions of the brain, including the peripheral white matter, globi pallidi, thalami, brainstem, dorsal pons, and dentate nuclei. The ADC values at these regions ranged from 0.42 to 0.56 x 10(-3) mm2/s compared with the normal ADC values from the uninvolved deep frontal white matter (0.68-0.92 x 10(-3) mm2/s). The known histopathologic features in Canavan disease include edematous and gelatinous brain tissue associated with diffuse vacuolization. Considering these and the diffusion MRI findings in this patient, it is likely that existence of a gel (gelatinous) state rather than the usual sol state of water molecules in the affected brain regions accounted for the restricted diffusion pattern in Canavan disease.

Idiopathic Localized Hydromyelia: Dilatation of the Central Canal of the Spinal Cord of Probable Congenital Origin

Three adult patients are reported with asymptomatic localized widening of the central canal of the spinal cord. These patients were followed for a period of 24 years by imaging and/or clinical history and physical examination without evidence of signs or symptoms related to the spinal cord. This condition probably represents persistence into adult life of a fetal configuration of the central canal of the spinal cord. This process may be termed idiopathic localized hydromyelia to distinguish it from syringomyelia secondary to such causes as Chiari malformation, trauma, infection, or neoplasm.

Recognition of abnormalities on computed scout images in CT examinations of the head and spine

SummaryWe investigated the information which can be obtained from the computer-generated digital radiographs (“scout images”) performed for CT examinations. One hundred CT examinations of the head and one hundred of the spine were randomly selected and retrospectively reviewed: the head scout images were acquired in the lateral projection, and those of the spine in the lateral and/or anteroposterior projections. In 122 patients with demonstrable pathology on the CT sections or the scout image, a total of 154 abnormalities was found, of which 31 (20%) were identified only on the scout images. Eight (25.8% of this number) required additional clinico-radiologic study and were therefore designated as clinically pertinent positives. This study demonstrates that the CT scout image may contain considerable, clinically relevant information which is not available on, or is complementary to, the CT sections.

Diffusion magnetic resonance imaging of solid vestibular schwannomas.

Six patients with solid vestibular schwannomas were studied by diffusion magnetic resonance imaging to assess if this modality adds new information for these tumors, because there is no previous report in the relevant literature. The sizes of the tumors ranged from 2.2 to 4.7 cm with respect to their largest diameters. They were isointense to the normal brain parenchyma on b = 1,000 s/mm2 images. The apparent diffusion coefficient (ADC) values in the tumors were high (range: 1.14-1.72 x 10(-3) mm2/s, mean = 1.42 +/- 0.17 x 10(-3) mm2/s) compared with normal brain parenchyma ADC values (mean = 0.80 +/- 0.11 x 10(-3) mm2/s). High ADC values of solid vestibular schwannomas were in conformity with increased diffusion rates, indicating the presence of increased amounts of extracellular water (a relatively loose tissue) in the tumor matrix.

The characteristics of cerebral meningiomas and surrounding tissues on dynamic CT

SummaryDynamic CT was utilized to evaluate 11 patients with histologically benign meningiomas. While it was found that all demonstrated macroscopic neovascularity, subtle differences in the dynamic perfusion curves were identified both between different meningiomas and from region to region within the same tumor. Other than basic anatomic differences, these changes may reflect intratumoral ischemia and hypothetically herald cystic/necrotic alteration within the neoplasm. The dynamic calculations over the surrounding brain showed areas of gross hyper- and hypoperfused cerebral cortex, and hypoperfused white matter in regions of peritumoral edema. These latter findings are of uncertain clinical importance. The dynamic examination also confirmed cases of dural venous sinus invasion and calvarial permeation by tumor. In addition, the dynamic series showed macroscopic neovascularity in one case with a completely negative selective cerebral arteriogram. It is felt that certain cases which have previously been evaluated by static CT may benefit from further study utilizing the dynamic method.

Phenylketonuria: diffusion magnetic resonance imaging and proton magnetic resonance spectroscopy.

Two patients with phenylketonuria are reported with white matter lesions. Diffusion magnetic resonance (MR) imaging revealed restricted diffusion patterns (high signal) on b = 1000 s/mm2 images associated with low apparent diffusion coefficient values ranging between 0.44 x 10-3 mm2/s and 0.56 x 10-3 mm2/s. On proton MR spectroscopy obtained in 1 of the patients, a prominent peak resonating at approximately 3.80 ppm was consistently present attributable to the peak rising from the alpha-proton of the phenylalanine molecule.

CT of intrasellar colloid cyst.

Colloid cysts are congenital lesions considered to be derived from the primitive neuroepithelium and are most frequently located in the anterior third ventricle. In this paper a case of colloid cyst with a intra/suprasellar location is presented. Computed tomographic characteristics of this lesion were strongly consistent with the classic features of colloid cysts, particularly when interpreted retrospectively after surgical and histopathological data became available. The unusual occurrence of a colloid cyst in this location supports the theory that epithelial cysts related to sella turcica are derived not solely from Rathke cleft but also from neuroepithelium.