Analysis of 25 patients who fulfilled clinical and radiographic criteria for the diagnosis of "normal pressure" hydrocephalus (NPH) demonstrated (1) a significant relationship between presence of motor signs with good outcome and absence of motor signs with poor outcome following ventricular shunting, (2) symptoms and signs of parkinsonism in 40% of patients in whom the diagnosis of NPH was made, and (3) no reliable relationship between radiographic measurements or cisternogram appearance and outcome following shunting. The clinical picture is the most important factor in selection of NPH patients for surgery.
Seventeen of 33 patients (51.5%) with normal pressure hydrocephalus were discovered to have diabetes mellitus. This was significantly greater than the 12.1% incidence found in age-matched control subjects. The diabetes was not accounted for either by the patients' ages nor by their physical inactivity due to hospitalisation. Diabetes mellitus concurrent with normal pressure hydrocephalus may result from involvement of hypothalamic and brainstem autonomic structures by the expanding ventricles during the evolution of hydrocephalus.
Seventy-nine autopsy correlations of CT scans showed (1) excellent correlations in normal brains, but the size of the lateral ventricles consistently larger during life than after death; (2) a distinctive pattern differentiating obstructive from nonobstructive hydrocephalus; (3) infarctions appearing as areas of decreased densities of parenchyma in vascular distributions; (4) distinctive high density appearances of hemorrhages that differentiated them from infarctions and, in general, all other pathologic processes; (5) supratentorial, intraventricular, and posterior fossa tumors appearing as masses that displaced, distorted, collapsed, and enlarged normal spaces and structures such as ventricles and pineal gland; (6) 11 false-negative CT scans in some cases of brain stem infarction, brain stem hemorrhage, and small metastasis; and (7) an overall accuracy of 86.2 percent of CT scanning in correctly identifying pathology of the brain.
Twenty patients with normal pressure hydrocephalus were examined by computerized axial transverse tomographic (CT) scanning and the results were compared with pneumoencephalographic findings and clinical responses to ventricular shunting. The CT scan revealed significant cortical atrophy, not demonstrated by pneumoencephalogram in seven patients. The cortical atrophy was confirmed by autopsy in one case. This examination also revealed greatly enlarged ventricles (25 to 40 percent of intracranial volume) in eight patients up to 4 years after ventricular shunting. There was no relationship between the presence or absence of cortical atrophy, or the postoperative ventricular size, and the clinical responses to ventricular shunting. Current concepts of normal pressure hydrocephalus must be revised in view of these findings.
One hundred eleven patients with supratentorial cerebrovascular disease were studied by computerized axial tomography (CT scanning). With one exception, every patient who had a normal scan 48 hours after the onset of symptoms was ultimately diagnosed as having had transient ischemic attack, although in nearly one-third, the clinical diagnoses at the time of the scan was infarction. A normal CT scan, therefore, augurs a good outcome of supratentorial cerebrovascular disease. Ninety-eight percent of the patients with infarction had abnormal scans, with areas of decreased density in a vascular distribution. Pitfalls in the diagnosis of infarction were (1) initially normal CT scans that changed to abnormal after 48 hours, and (2) mass effect of infarction leading to misdiagnosis of brain tumor. Serial studies eliminated both pitfalls. Intracerebral hemorrhages had a distinctive high density appearance. In 43 percent of patients whose scans showed hemorrhage, the clinical diagnosis was thrombosis. Many did not have symptoms, signs, or outcome of cerebral hemorrhage, and the diagnosis would not have been suspect were it not for the CT scan.
An important computerized tomographic (CT) pattern is described, in which selective enhancement of cerebral gray matter occurs after intravenous administration of contrast medium. Analysis of 76 cases displaying the enhancement pattern revealed that the phenomenon occurs in diseases characterized by hypoxia, and may be attributed to regional vascular dysautoregulation. Eighty percent of these patients had primary cerebrovascular disease (infarctions or transient ischemic attacks); 20% with other disorders also had evidence of cerebral ischemia or infarction. When hypoxia progressed to infarction, the enhancement was accompanied by one or more parenchymal areas of decreased density. However, in transient ischemic attacks, it occurred without other parenchymal abnormality and represents the first recognized CT sign of cerebral hypoxia. Enhancement was observed within 3 weeks of onset in 80% of cases, but in 20% it persisted for up to 4 months, indicating a protracted state of dysautoregulation.
