Second-day encephalography, with particular reference to the size of the ventricles

Intracranial pressure during ventriculography using meglumine iothalamate

A small increase in ventricular fluid pressure (1.3 +/- 0.3 mm Hg) occurs on isovolumetic addition of meglumine iothalamate to the lateral ventricle. A marked increase (46.3 +/- 3.2 mm Hg: P less than 0.001) in pressure occurs on passage of the contrast medium into the posterior part of the third ventricle; the aqueduct and the fourth ventricle. Theoretical mechanisms are discussed.

Effect of intracranial pressure of meglumine iothalamate ventriculography

Intraventricular pressure was studied in 12 patients undergoing ventriculography with a water soluble positive contrast medium. Isovolumetric instillation of meglumine iothalamate into the lateral ventricles and the anterior part of the third ventricle caused only a small increase in ventricular fluid pressure (1.3 +/- 0.3 mmHg), but the pressure increased markedly (46.3 +/- 3.7 mmHg; P less than 0.001) when the contrast medium entered the posterior end of the third ventricle, aqueduct of Sylvius,, and fourth ventricle. This sharp increase in intracranial pressure could not be attributed solely to the postural changes or to alterations in arterial blood pressure. Possible mechanisms are discussed.

The twenty-four hour pneumoencephalogram: with particular reference to ventricular size a series of 150 patients and a review of the literature

A series of 150 pneumoencephalograms which included 24 h films was reviewed to evaluate previous contradictory reports concerning changes in ventricular size at 24 h and to establish whether it is useful to obtain these follow-up films. In normal patients the changes in the ventricular index one day following the pneumoencephalogram ranged between -4-1 to +6-4% of the initial index. Statistically significant dilatation of the frontal horns of the lateral ventricles was observed in both patients who had dementia and central atrophy, and in those with normal pressure hydrocephalus. This ventricular enlargement was associated with deterioration in neurological status in some cases. Since ventricular enlargement at 24 h occurs in patients both with normal pressure hydrocephalus and with cerebral atrophy with hydrocephalus, it cannot be used to differentiate between these conditions although the most marked changes have been seen in the former. Significant dilatation did not occur in patients without intracranial disease, with cortical atrophy without hydrocephalus, or in a miscellaneous group. In patients with a history of trauma, enlargement at 24 h occurred only when there was some other encephalographic abnormality. The changes in size of the ventricles were not related to the age of the patient, the volume of the injected air, or to the presnece of subdural air. There were other findings on the follow=up radiographs. Cortical atrophy was more clearly demonstrated than on the filling films. Dilatation of the temporal horns, of questionable diagnostic significance, was not infrequently observed 24 h after air injection. The mechanisms of these changes are discussed; no single theory provides a complete explanation.

The effect of intraventricular air on the rate of cerebrospinal fluid formation in dogs

✓ Experiments were performed on dogs to estimate the effect of intraventricular air on the rate of cerebrospinal fluid formation. The rate of formation was measured satisfactorily in eight beagle dogs before and after the introduction of air using ventriculocisternal perfusion of artificial cerebrospinal fluid containing 14C-labelled inulin. Statistical analysis of rates of cerebrospinal fluid formation estimated half hourly indicated that there was little or no change after the introduction of air.

Progressive ventricular dilatation following pneumonencephalography. A radiological sign of occult hydrocephalus

✓ Eight patients with “normal pressure hydrocephalus” are presented who demonstrated radiographic and occasional clinical evidence of progressive dilatation of the ventricles following pneumoencephalography. The characteristic pneumographic signs of tentorial obstruction to the flow of cerebrospinal fluid (CSF) had been documented in the original air contrast study. The authors postulate that pneumoencephalography in patients with normal pressure hydrocephalus may result in a sudden displacement of CSF from the ventricles into the already compromised basal cisterns, leading to further obstruction of CSF outflow and progressive ventricular dilatation. Other mechanisms such as reduction in the potential resorptive capacity of the ventricular ependyma by air replacing ventricular fluid may play a part. The value of repeat radiological studies 24 and 48 hours after the original pneumogram is emphasized both as an aid in the radiological diagnosis of normal pressure hydrocephalus and as an additional parameter for studying problems in CSF flow and absorption.