Radiation-induced optic neuropathy: correlation of MR imaging and radiation dosimetry

The authors performed topographic correlation of dosimetric measurements with contrast medium-enhanced magnetic resonance (MR) imaging signal aberration in two cases of radiation optic neuropathy. The region of pathologic contrast enhancement in the optic nerve and chiasm had received 55-62 Gy, which supports the theory that the risk of injury to the optic nerve and chiasm increases steeply with radiation doses above the tolerance level of 50-55 Gy.

Hippocampal formation volume, memory dysfunction, and cortisol levels in patients with Cushing's syndrome

Patients with chronic hypercortisolemia due to Cushing's syndrome (CS) exhibit cognitive dysfunction. Because glucocorticoid excess is associated with hippocampal damage in animals, and the hippocampus participates in learning and memory, we explored the relationships between hippocampal formation (HF) volume, memory dysfunction, and cortisol levels in 12 patients with CS. After magnetic resonance imaging, HF volume was determined using digital sum of track ball traces of dentate gyrus, hippocampus proper and subiculum, correcting for total intracranial volume. For 27% of the patients, HF volume fell outside the 95% confidence intervals for normal subject volume given in the literature. In addition, there were significant and specific correlations between HF volume and scores for verbal paired associate learning, verbal recall, and verbal recall corrected for full-scale IQ (r = 0.57 to 0.70, p < 0.05). HF volume was negatively correlated with plasma cortisol levels (r = -0.73, p < 0.05). These studies suggest an association between reduced HF volume, memory dysfunction, and elevated cortisol in patients with CS.

Enhancement along the normal facial nerve in the facial canal: MR imaging and anatomic correlation

Normal facial nerves are reported to show no enhancement at magnetic resonance (MR) imaging, in contradiction to the authors' clinical experience. To investigate this inconsistency, the authors searched MR imaging files and clinical records to find patients who underwent MR imaging of the temporal bone (at 1.5 T) before and after intravenous administration of gadopentetate dimeglumine and who had bilateral clinically normal facial nerves. When the MR images of 93 patients (186 facial nerves) were analyzed subjectively, 142 nerves (76%) were visibly enhanced along at least one segment of the facial nerve within the facial canal; the nerves of 64 of the 93 patients (69%) showed right-left asymmetry in enhancement, which was inhomogeneously distributed along each nerve. The facial nerve in the cerebellopontine angle cistern and in the internal auditory canal, as well as in the visualized proximal portion of the extracranial facial nerve, showed no enhancement. Comparison with reference anatomic sections showed that this enhancement pattern corresponded exactly to the topography of the circumneural facial arteriovenous plexus and should not necessarily be considered a sign of anatomic abnormality.

Visual loss in tuberous sclerosis

Of 11 patients with tuberous sclerosis complex (TSC) treated from 1980 to 1990 for obstructive hydrocephalus secondary to subependymal giant-cell astrocytoma, four had adequate documentation to determine visual outcome. Despite surgical relief of elevated intracranial pressure in all cases, two patients sustained further visual loss. In one patient, visual loss was arrested, and in one patient, it was prevented. Although hydrocephalus is uncommon in TSC, its effects on the optic nerves are serious and eventually irreversible. Because TSC patients may not be able to express early symptoms of increased intracranial pressure, periodic ophthalmologic examination and brain imaging may be advisable when a subependymal lesion has been identified.

Nystagmus of Pelizaeus-Merzbacher disease. A magnetic search-coil study

Magnetic search-coil oculography of three brothers with clinically diagnosed Pelizaeus-Merzbacher disease disclosed the presence of binocular elliptical pendular nystagmus in two patients in whom the waveform of the nystagmus was not obvious on inspection. This study, the first reported application of high-resolution oculography to Pelizaeus-Merzbacher disease, also demonstrated primary position upbeat nystagmus in all three patients. The importance of finding this combination of elliptical pendular and upbeat nystagmus is that it is not described in any other childhood neurodegenerative states and, in combination with supportive clinical history and magnetic resonance imaging, may be so characteristic of Pelizaeus-Merzbacher disease that a strong presumptive diagnosis can be made.

Three-dimensional x-ray computed tomography of the temporal bone as an aid to surgical planning

Three-dimensional x-ray computed tomography (3DCT) has been useful in planning surgical procedures involving craniofacial reconstruction, the pelvis, hip, spine, knee and shoulder. The clinical use of 3DCT in temporal bone surgery has not been evaluated. We used 3DCT to assess temporal bone anatomy in 9 patients. These cases evaluated two encephaloceles, two postinflammatory dehiscences, two temporal bone fractures, one glomus jugulare tumor, one acoustic neuroma, and one meningioma. We found 3DCT useful in these temporal bone applications as a supplement to standard two-dimensional CT scanning (2DCT). While 3DCT provided a better preoperative understanding of the underlying anatomy, no treatment was modified solely on the basis of the information derived from the 3-D presentation of data. We conclude that, although 3DCT images have some qualitative advantages over 2DCT techniques, their value in further defining temporal bone morphology must be evaluated against the cost entailed by their use.

The Marinesco-Sjögren syndrome examined by computed tomography, magnetic resonance, and 18F-2-fluoro-2-deoxy-D-glucose and positron emission tomography

The Marinesco-Sjögren syndrome is an autosomal recessive degenerative disorder characterized by congenital cataracts, cerebellar ataxia, spasticity, mental deficiency, and skeletal abnormalities. We studied two adult siblings with Marinesco-Sjögren syndrome using anatomic and metabolic brain imaging techniques to characterize the pattern and nature of abnormalities in the brain. Computed tomographic and magnetic resonance imaging showed diffuse brain atrophy of mild to moderate degree, involving primarily the white matter of the cerebrum, cerebellum, brain stem, and cervical spinal cord. The pattern of atrophy resembled that seen in diffuse leukoencephalopathies. Measurements of local cerebral glucose metabolic rates with positron emission tomography revealed no statistically significant differences from normal control subjects in most regions, but metabolic rate was decreased in the thalamus in one patient. The findings support a diffuse white matter disorder in Marinesco-Sjögren syndrome.

Intra-arterial bromodeoxyuridine radiosensitization of malignant gliomas

In the 1950's it was first observed that mammalian cells exposed to the halogenated deoxyuridines were more sensitive to ultraviolet light and radiation than untreated cells. This prompted early clinical trials with bromodeoxyuridine (BUdR) which showed mixed results. More recently, several Phase I studies, while establishing the feasibility of continuous intravenous (IV) infusion of BUdR, have reported significant dose limiting skin and bone marrow toxicities and have questioned the optimal method of BUdR delivery. To exploit the high mitotic activity of malignant gliomas relative to surrounding normal brain tissue, we have developed a permanently implantable infusion pump system for safe, continuous intraarterial (IA) internal carotid BUdR delivery. Since July 1985, 23 patients with malignant brain tumors (18 grade 4, 5 grade 3) have been treated in a Phase I clinical trial using IA BUdR (400-600 mg/m2/day X 8 1/2 weeks) and focal external beam radiotherapy (59.4 Gy at 1.8 Gy/day in 6 1/2 weeks). Following initial biopsy/surgery the infusion pump system was implanted; BUdR infusion began 2 weeks prior to and continued throughout the 6 1/2 week course of radiotherapy. There have been no vascular complications. Side-effects in all patients have included varying degrees of anorexia, fatigue, ipsilateral forehead dermatitis, blepharitis, and conjunctivitis. Myelosuppression requiring dose reduction occurred in one patient. An overall Kaplan-Meier estimated median survival of 20 months has been achieved. As in larger controlled series, histologic grade and age are prognostically significant. We have shown in a Phase I study that IA BUdR radiosensitization is safe, tolerable, may lead to improved survival, and appears to be an efficacious primary treatment of malignant gliomas.

MR imaging of the brain in five members of a family with Pelizaeus-Merzbacher disease

MR imaging was performed in five members of a family afflicted with Pelizaeus-Merzbacher disease. The individuals imaged included a male proband, his mother, and three maternal uncles. Clinically affected members showed generalized white matter signal aberration consistent with dys- and demyelination, basal ganglia, and thalamic signal aberration suggestive of pathologic iron storage and diffuse brain atrophy. These findings are similar to those seen in other leukodystrophies. The proband's mother was normal by neurologic examination but showed a suspicious but not definitely abnormal similar pattern of basal ganglionic and white matter signal aberration. In our limited patient sample, MR appears to be able to: (1) demonstrate a pattern of imaging abnormalities characteristic of Pelizaeus-Merzbacher disease (we do not know if this pattern is specific); (2) potentially detect the obligate carrier state; and (3) detect the facultative carrier state.

Cranial lymphangiomatosis causing CSF otorrhea and recurrent meningitis: CT features

We present a case of cranial lymphangiomatosis that resulted in CSF leakage through the ear and recurrent meningitis. The plain radiographic findings, CT, and CT cisternographic appearances are discussed along with a brief review of the literature.

Visual outcome in cystic craniopharyngiomas treated with intracavitary phosphorus-32

Seven patients with cystic craniopharyngiomas were treated with stereotactic instillation of radioactive phosphorus-32 (32P). Five patients had been previously treated with various combinations of surgery and external beam irradiation, whereas two had the 32P instillation at a primary therapy. Visual acuity improved in 13 eyes and remained stable in 1. Visual fields normalized in three patients, improved in two, and remained stable in two. Two patients received single treatments with 32P, whereas five required multiple instillations for recurrent cyst expansion.

Optic tract injury after anterior temporal lobectomy

Three patients had complete homonymous hemianopia with clinical and neuroimaging characteristics of ipsilateral optic tract infarction after anterior temporal lobectomy for seizure control. This injury presumably resulted from irritative vasospasm of the anterior choroidal artery. The features of this pure optic tract syndrome should be distinguished from the more common compressive optic tract syndrome which generally also impairs ipsilateral optic nerve function.

CT demonstration of cavernous sinus fat

CT demonstration of cavernous sinus fat deposits has been described as abnormal and potentially a specific sign of Cushing disease. CT scans of 100 patients without biochemical or clinical evidence of Cushing disease and of 10 patients with Cushing disease were studied retrospectively. Twenty-seven percent of the non-Cushing patients demonstrated fat in one or both cavernous sinuses. Forty percent of Cushing disease patients had detectable cavernous sinus fat. While fat deposits were more frequent in the Cushing disease group, this was not statistically significant (p = greater than .6). CT demonstration of cavernous sinus fat ordinarily should be regarded as a normal finding.

Atlanto-axial rotational limitation secondary to osteoid osteoma of the axis. Case report

An unusual case of atlanto-axial rotational limitation secondary to an osteoid osteoma of the axis is presented. Transoral microsurgical resection followed by physical therapy improved the clinical symptoms. This case illustrates several unique problems within the cervical spine as well as the efficacy of the transoral approach to the axis.

Idiopathic intracranial hypertension (pseudotumor cerebri): MR imaging

Magnetic resonance (MR) imaging was performed on six patients with idiopathic intracranial hypertension (IIH). The patients were all women with a mean age of 27 years (range, 17-41 years). Six healthy women volunteers with a mean age of 33 years (range, 25-46 years) were studied for comparison. All six patients had elevated opening pressures at lumbar puncture. MR imaging demonstrated a partially empty sella in two patients, and one patient had signal aberration in the dural venous sinuses suggestive of slow flow. There were no white matter signal abnormalities, even in the periependymal space. Volumetric pixel analysis revealed significantly larger subarachnoid space volumes in patients than in control subjects, without a significant difference in ventricular volumes. No other intracranial abnormalities were found in any IIH patient or control subject. The results suggest that, in IIH, (a) although the subarachnoid spaces are enlarged, the wide range of normal values would limit the clinical use of these measurements and (b) the role of MR imaging, as with CT, is primarily in the exclusion of other diseases with clinical presentations similar to that of IIH.

Intra-arterial 5-bromo-2-deoxyuridine (BUdR) radiosensitization with external beam radiation in rhesus monkeys: toxicity study

A primate toxicity study was performed to test the hypothesis that BUdR does not increase the likelihood of unilateral or bilateral central nervous system damage secondary to radiation therapy. BUdR, a halogenated pyrimidine analog is incorporated into DNA of dividing cells and sensitizes them to radiation. It is best given unilaterally, intra-arterially by continuous infusion because of its regional advantage (Rd) estimated to be between 11 and 16. Six rhesus monkeys were implanted with a Model 400 Infusaid pump perfusing the right internal carotid artery. Three of the six monkeys received intra-arterial (IA) BUdR infusion plus whole brain external beam radiation (6,000 R over 6 weeks) and three received radiation alone. The two BUdR treated animals completing radiation developed symmetric bilateral high signal aberrations on MRI in the frontal, parietal, and occipital centrum semiovale and corona radiata at nine months. At autopsy, confluent microinfarcts were found to correspond topographically to the MRI abnormalities. In the radiation alone group, two animals had normal MRI and autopsy while the third animal had bilateral MRI high signal aberrations develop sequentially with corresponding microinfarcts at autopsy. These changes were greater in severity than those seen in the BUdR treated animals. We support previous evidence that there is differential intraspecies sensitivity to radiation. We find that BUdR produces no unilateral potentiation of radiation toxicity.

Preoperative treatment of acromegaly with long-acting somatostatin analog SMS 201-995: shrinkage of invasive pituitary macroadenomas and improved surgical remission rate

Ten patients with previously untreated acromegaly and invasive pituitary macroadenomas were treated with the long-acting somatostatin analog SMS 201-995 (Sandoz) for 3-30 weeks before transsphenoidal or subfrontal pituitary adenomectomy. Preoperatively, treatment with SMS 201-995 reduced mean 24-h plasma GH concentrations from 8.5-66.7 to below 4.6 micrograms/L in eight patients and by 60-80% in the remaining two patients. Pituitary tumor size decreased 20-54%. Morphologically, the tumors showed decreased total cell, cytoplasmic, and nuclear areas; varying degrees of perivascular fibrosis; and dense granularity. Postoperatively, plasma GH and insulin-like growth factor I concentrations fell into the normal range, and GH dynamics became normal in eight patients. In the remaining two patients mild GH hypersecretion persisted after surgery (mean fasting and random plasma GH, 6.1 and 7.9 micrograms/L), and in one of them GH secretion became normal 1 yr after pituitary irradiation. Thus, preoperative administration of SMS 201-995 consistently induced shrinkage of GH-producing pituitary tumors, and the apparent remission rate was high in the treated patients.

Intra-arterial bromodeoxyuridine radiosensitization and radiation in treatment of malignant astrocytomas

Bromodeoxyuridine (BUdR), a nonhypoxic radiosensitizing drug, is a halogenated pyrimidine analog that is incorporated into the deoxyribonucleic acid of dividing cells in a competitive process with thymidine; BUdR also sensitizes these cells to radiation therapy. Neurons and glial cells have a very low mitotic rate. They will not incorporate BUdR and will not be sensitized. Bromodeoxyuridine is best delivered intra-arterially because of its regional advantage, calculated to be between 6 and 16. An 8-week BUdR infusion is delivered before and during radiation therapy through a permanently implanted pump with a catheter placed retrograde into the external carotid artery. Eighteen patients with malignant glioma (15 grade IV, and three grade III) were entered into a Phase I dose-escalation protocol with BUdR dosages ranging from 400 to 600 mg/sq m/day. The maximum dose that can be tolerated appears to be 400 mg/sq m/day for 8 weeks. The 18 patients entered in this study have a median Kaplan-Meier estimated survival time (+/- standard error of the mean) of 22 +/- 5 months with 11 patients still alive. Three patients are alive at 30, 29, and 21 months after diagnosis with no evidence of tumor on computerized tomography. There have been no vascular complications. Side effects in all patients have included anorexia, fatigue, ipsilateral forehead dermatitis, blepharitis, iritis, and nail ridging. Myelosuppression requiring dose reduction occurred in one patient. One patient had a Stevens-Johnson syndrome requiring termination of BUdR. It is concluded that intra-arterial BUdR may improve survival times in patients with malignant gliomas.

Motor dysfunction in olivopontocerebellar atrophy is related to cerebral metabolic rate studied with positron emission tomography

We compared the severity of motor dysfunction with local cerebral metabolic rates for glucose (lCMRGlc) and the degree of tissue atrophy in 30 patients with olivopontocerebellar atrophy (OPCA). We devised a scale to quantitate the degree of ataxia in the neurological examinations. lCMRGlc was measured with 18F-2-fluoro-2-deoxy-D-glucose and positron emission tomography (PET). Tissue atrophy was assessed by visual rating of computed tomographic scans. PET studies revealed marked hypometabolism in the cerebellar vermis, cerebellar hemispheres, and brainstem of OPCA patients compared with 30 control subjects. A significant correlation was found between severity of motor impairment and lCMRGlc within the cerebellar vermis, both cerebellar hemispheres, and the brainstem. A significant but weaker relationship was noted between the degree of tissue atrophy in these regions and clinical severity. Partial correlation analysis revealed that motor dysfunction in OPCA correlated more strongly with lCMRGlc than with the amount of tissue atrophy. These results suggest that the clinical manifestations of OPCA are more closely related to the metabolic state of the tissue than to the structural changes in the cerebellum.

Cerebellar and brainstem hypometabolism in olivopontocerebellar atrophy detected with positron emission tomography

We studied local cerebral metabolic rates for glucose (1CMRglc) with 18F-2-fluoro-2-deoxy-D-glucose and positron emission tomography (PET) in 30 patients with olivopontocerebellar atrophy (OPCA) and 30 age-matched control subjects without neurological disease. The diagnosis of OPCA was based on the history and physical findings and on the exclusion of other causes of cerebellar ataxia by means of laboratory investigations. Computed tomographic scans revealed some degree of atrophy of the cerebellum in most patients with OPCA, and many also had atrophy of the brainstem. PET studies in these patients revealed significant hypometabolism in the cerebellar hemispheres, cerebellar vermis, and brainstem in comparison with the normal control subjects. A significant relationship was found between the degree of atrophy and the level of 1CMRglc in the cerebellum and brainstem. Nevertheless, several patients had minimal atrophy and substantially reduced 1CMRglc, suggesting that atrophy does not fully account for the finding of hypometabolism. 1CMRglc was within normal limits for the thalamus and cerebral cortex. The data suggest that PET/1CMRglc may be useful as a diagnostic test in patients with the adult onset of cerebellar ataxia.

MR imaging of Pelizaeus-Merzbacher disease

Pelizaeus-Merzbacher disease (PMD) is a rare, slowly progressive, sex-linked demyelinating disorder generally classified with the sudanophilic leukodystrophies. The onset is most often in the pediatric age group and may be diagnosed as cerebral palsy because of the subtle onset. Cranial magnetic resonance (MR) imaging of two patients with PMD showed reversal of the normal gray/white matter signal relationships, consistent with dysmyelination, as well as low intensity lentiform nuclei and thalami possibly suggesting pathologic iron deposition. Magnetic resonance also better demonstrated low volume brain without the beam hardening limitations of X-ray CT. Although our MR findings correlate well with the pathophysiology of PMD, the MR characteristics are not specific. The diagnosis of PMD remains one of clinical and laboratory exclusion.