B. E. Kendall

Surgical treatment of giant pituitary adenomas.

Multidirectional extension and invasive spread are important features of giant pituitary adenomas. Operability cannot be established merely by determining the size of the most prominent part of the tumour. Detailed radiological evaluation with plain films, computed tomography, angiography, and air studies all contribute to evaluation of the precise anatomy before surgery. In the final decision risks of surgical treatment must be balanced against the patients age and prospects of long-term useful survival. Unfavourable cases for surgical treatment in our hands were those tumours embedded in the hypothalamus with thalamic and posterior extensions. Partial removal of such cases gave poor results. Where the mass proves soft, radical excision may be possible, but not otherwise. Limited biopsy for histological study, followed by a shunt procedure and x-ray therapy seems still the only recourse.

Disseminated lesions at presentation in patients with optic neuritis.

Thirty five adults and two children with clinically isolated optic neuritis were examined by magnetic resonance imaging (MRI) to determine the presence of disseminated lesions within the brain at presentation and to compare these findings with the results of evoked potential studies. Of the adult patients, 61% showed lesions on the scans whereas the evoked potentials suggested the presence of lesions outside the visual system in 30%. MRI is a sensitive method for the demonstration of clinically unsuspected lesions in patients with uncomplicated optic neuritis.

Computed tomography in cervical spondylotic myelopathy and radiculopathy: visualisation of structures, myelographic comparison, cord measurements and clinical utility

SummarySixty-nine patients with cervical spondylotic myelopathy (CSM), radiculopathy (CSR), or both (CSMR) were studied with computed tomography (CT). Computer-assisted myelography (CAM) accurately determines the site and nature of spondylotic protrusions and provides good visualisation of the subarachnoid space and cord deformities even in areas with dilute metrizamide. However, excessive vertebral movement and bulging ligamenta flava with their effects on cord deformity, so easily visualised in myelograms, are completely or partially missed. In the assessment of CSM, metrizamide myelography (MM) followed by CAM should be performed, particularly when the myelographic images are unsatisfactory due to contrast dilution or blockage, when cord compression cannot be ascertained with MM and when cord atrophy is suspected. In CSR, the diagnostic information from MM and CAM is comparable. The diagnostic criteria in CAM are, however, less direct and since MM is adequate in uncomplicated cases, CAM is generally not necessary. The APD, APD/TD ratio, area and circularity are sensitive indices of cord deformity and the first two should be used more often to assist visual assessment of cord deformity. The relation between cord parameters and treatment response is better reflected in CSM cases managed conservatively and the results suggest that the degree of cord deformity is helpful in determining the outcome and hence the choice between surgical and conservative treatment. In plain CT, the osteophytes and calcified discs are adequately visualised and canal dimensions measured with accuracy, but the cervical cord and roots cannot be properly assessed and the diagnosis of CSM or CSR cannot be ascertained. At present, its role in cervical spondylosis is therefore limited.

Responses of baboon cerebral and extracerebral arteries to prostacyclin and prostaglandin endoperoxide in vitro and in vivo.

The responses of baboon cerebral and extracerebral arteries to prostaglandin endoperoxide (PGH2) and prostacyclin (PGI2) were investigated on isolated arteries and in vivo by serial angiography. Both PGH2 and PGI2 could produce dose-dependent contraction or relaxation of isolated arteries. PGH2 induced relaxation was indicative of prostacyclin synthetase activity, the enzyme which converts PGH2 to PGI2. In isolated arteries tested one to four hours post mortem only the vertebral artery showed prostacyclin synthetase activity. Thus PGH2 induced contraction of cerebral arteries may be indicative of a physiological function. Vasomotor tone may in part be the result of a balance between PGH2 constriction and PGI2 dilatation. In vivo PGI2 infusion caused pronounced and prolonged dilatation of cerebral arteries, which lasted longer than the cardiovascular changes. As PGI2 is the most potent cerebral vasodilator drug tested, it may be of clinical use in the treatment of cerebral vasospasm.

Difficulties in diagnosis of supratentorial gliomas by CAT scan.

The false positive and false negative computed tomography diagnoses of glioma made using an EMI 1010 machine on a consecutive series of patients seen over a period of two years are recorded. About 1.5% of gliomas were not detected on initial CAT scan, 6.5% were misdiagnosed as benign lesions, and in 6.5% of the cases identified as glioma a non-malignant condition was subsequently diagnosed.

Relationship between visual field defect and arterial occlusion in the posterior cerebral circulation

(1) The extent and severity of visual field loss has been compared in a series of 14 patients with occlusions of the posterior cerebral artery or its branches, all verified angiographically. Atheroma, embolism, and migraine were the commonest types of underlying vascular disease. (2) Occlusion of the main trunk of the artery was associated with severe and permanent field loss usually with some sparing of the central area and, in one case, of some field adjacent to the vertical meridian. It is suggested that this is due to collateral blood flow reaching the margins of the posterior cerebral territory from the adjacent middle cerebral territory via pial anastomoses. (3) Single or multiple occlusions of the main branches of the posterior cerebral artery gave variable amounts of field loss with considerable recovery in some cases. Collateral blood flow from the middle cerebral territory and from other branches of the posterior cerebral artery was demonstrated and the variation may be due to the size and number of pial anastomoses and to systemic factors such as blood pressure and vascular reactivity. (4) Occlusion of smaller branches of the calcarine artery produced localized zones of capillary underperfusion near the posterior cerebral pole. These corresponded to scotomatous paracentral defects in the visual field which were often permanent and showed no central sparing. The potential capacity of the collateral system may be limited by occlusion of intracerebral arteries or by involvement of segments of the pial arteries in the disease process.

Morphology and measurements of the cervical spinal cord in computer-assisted myelography

SummaryThirty-six control subjects had computer assisted myelography (CAM) using the EMI CT 5005 scanner. The normal cervical cord is elliptical, more circular at the upper and lower ends and flatter in the mid-segments. Asymptomatic cord deformities, usually mild, were present in nine subjects (25%). Four measurements, namely, sagittal diameter (APD), transverse diameter (TD), area (a) and circumference (c) were made and two more parameters calcultted i.e. APD/TD ratio and circularity (=4 π a/c2). These control values form the basis of qualitative and quantitative assessment of cord deformity. When cord measurements are to be used, control values should be obtained for each scanner and procedures should be standardized

Difficulties in diagnosis of intracranial meningiomas by computed tomography.

The false positive and false negative computed tomography diagnoses of meningioma made using EMI 1010 and 5005 machines on a consecutive series of patients seen over a period of four years are described. About 1.2% of intracranial meningiomas were not detected on initial CT scan, 6.6% were misdiagnosed including 5.2% which were thought to be malignant lesions; in 9.4% of the cases identified as meningioma another diagnosis was subsequently established of which 6.3% were malignant.

Xenon enhancement for computed tomography of the spinal cord.

SummaryThe spinal cord is not consistently shown by plain computed tomography or with iodide enhancement. Xenon enhancement increases the attenuation of the spinal cord and visualization is improved considerably; fluid-filled cavities, including syringohydromyelia, do not enhance and are clearly defined.

The Diagnostic Limitations of Computerised Axial Tomography in Hemispheric Tumours

We have reviewed the first 6,500 CT scans (Table 1.1.) made in the National Hospital with the 160 x 160 matrix EMI head scanner with a view to establishing its accuracy and limitations in routine clinical practice in the diagnosis and management of suspected intracerebral tumours, and to verifying the diagnostic criteria which have been used throughout this period. We analysed the original radiological reports which had been made with some limited clinical data and, in some cases, with the knowledge of findings from other radiological investigations. The scans of these patients, on which a CT diagnosis of an intracerebral tumour had been made or included in the differential diagnosis, and the scans of all patients in whom an intracerebral tumour had been histologically proven during the same period were retrospectively analysed by one of us (EC) without any other information, and finally they were reviewed in conjunction with the clinical findings but without any other data in order to see to what extent this altered the results.