Infratentorial Pressure Research Articles

Central Brain Herniation Secondary to Influenza-Related Encephalopathy in a Pontocerebellar Hypoplasia Child: A Case Report and Review

Influenza-associated encephalopathy (IAE) can perform as varying patterns of neuroimaging. Central brain herniation (CBH) secondary to IAE is rare; it may be a bad prognosis. Here, we presented a 4-year-old girl with influenza who had a pontocerebellar hypoplasia (PCH) history; she performed the second Magnetic Resonance Imaging (MRI) on Day 6 from onset, showed the diffuse edema and the occurrence of central herniation; the medulla was “Z-like” folded and the basal cisterns were obliterated completely. Finally she was declared dead. The imbalance between supratentorial and infratentorial pressure can lead to the occurrence of CBH. Severe edema relates to IAE and unstable structure of the posterior fossa might be the main reason for the herniation. MRI is helpful in early diagnosis. Early treatment of cerebral edema in patients with congenital abnormalities of the posterior fossa is vital for their management.

Dispersion of cerebral temperature, cerebral perfusion and intracranial pressure in rabbits placed with epidural balloons

This study examines the intracranial pressure and temperature dispersion in a rabbit model after epidural balloon compression. Right and left supratentorial, intraventricular and infratentorial pressures and temperatures of the rabbits have been measured before epidural balloon was placed. Afterwards, the epidural balloon was placed in right parietal epidural area. The intracranial pressure and temperature dispersion values were recorded after inflation with 0.3 and 0.6 ml, respectively. The control values of intracranial pressure measurements of four different brain regions were found to be similar. When the balloon was inflated to 0.3 ml, the intracranial pressure distribution was found to be equal in all the fields. After the balloon was inflated up to 0.6 ml, right and left supratentorial intracranial pressure values were found to be equal. However, infratentorial pressure values were lower and intraventricular pressure values were higher when compared with the right hemisphere. Before the inflation and at two different inflation volumes, perfusion pressure and temperature dispersion were found to be similar between right hemisphere and other compartments. We conclude that, the effective mechanism in cerebral temperature regulation may be related to preserved cerebral perfusion pressure and cerebral blood flow.

Cerebrovascular response to elevation of ventricular pressure.

The behaviour of Pial vessels to levels of CSF-pressure between 10 and 100 mmHg induced by vetricular infusion of mock CSF, was observed in 6 cats under barbiturate and N2O anaesthesia, using the cranial window technique and videoangiometry. Supratentorial pressure (STP) equaled infratentorial pressure in the cisterna magna (CMP) throughou. No changes in pial arterial calibres were noted up to a CMP of 13 mmHg (i.e. a cerebral perfusion pressure (CPP) of 100 mmHg). Further increase of CMP to 45 mmHg induced significant arterial dilatation of 40 +/- 3.4%. With a further rise of ventricular fluid pressure (VFP) no marked further arterial dilatation occurred. Dilatation of arteries up to 100 um resting diameter and arteries between 100 and 250 um resting diameter and arteries between 100 and 250 um was not significantly different. When CPP approached 40 mmHg, arteries were still 47 +/- 3.6% dilated. Pial venous calibre did not vary by more than 20% during elevation of VFP. At CPP 47 mmHg, small and large veins were dilated by 14%. Single venous segments were compressed by crossing pial arteries and caused upstream venous congestion and distension.

Pathophysiology of aqueductal obstruction in isolated IV ventricle after shunting.

The authors report their cases of isolated IV ventricle and discuss their concepts of secondary obstruction of the aqueduct, analyzing CSF dynamics, pressure measurements, serial CT scan changes, and the outcome of various treatment modalities. Two distinctly different categories were identified: functional obstruction in which the obstructed aqueduct reopened either as the result of decreasing the elevated infratentorial pressure (Raimondi's phenomenon) or from correction of overdrainage of the supratentorial system; permanent obstruction with pathological occlusion of the aqueduct, necessitating a IV ventriculoperitoneal shunt. It is the pathophysiology and pathoanatomy of secondary obstruction of the aqueduct that determine the specific treatment to be used in managing the isolated IV ventricle syndrome.

Acute intracranial hypertension and brain-stem blood flow. An experimental study.

This study has been carried out to evaluate the effect of supratentorial mass lesions on the local cerebral blood flow (CBF) of the brain stem. Local CBF of the thalamus, inferior colliculus, and medulla oblongata, and supra- and infratentorial pressure were serially measured in 52 cats with intracranial hypertension produced by supratentorial balloon expansion. The mean control local CBF's in the thalamus, inferior colliculus, and medulla oblongata were 37.5, 42.1, and 30.7 ml/100 gm/min, respectively. At 20 to 30 mm Hg of supratentorial pressure, the local CBF of the thalamus started to decrease, and at 20 mm Hg of infratentorial pressure, the local CBF of the inferior colliculus began to decrease. Finally, at 40 to 60 mm Hg of infratentorial pressure, the local CBF of the medulla oblongata was affected. At the beginning of uncal herniation, indicated by anisocoria, the mean local CBF of the inferior colliculus abruptly decreased from 33.7 to 19.6 ml/100 gm/min in 16 cats. The Cushing response was evoked at a mean supratentorial pressure of 93.4 mm Hg and infratentorial pressure of 49.9 mm Hg in 16 cats. When the systemic arterial pressure was increased to the highest level in 13 cats, the mean local CBF of the medulla oblongata did not show significant change (a decrease from 22.8 to 20.9 ml/100 gm/min). The results suggest that at the beginning of uncal herniation, the local CBF of the upper brain stem markedly decreased. During the Cushing response, the local CBF of the medulla oblongata did not change significantly.

Changes in local blood flow of the brain stem in acute intracranial hypertension. Experimental study

The effect of supratentorial mass lesions on the local cerebral blood flow (1CBF) of the brain-stem was evaluated with special reference to the following three points. 1) The level of the intracranial pressure (ICP) at which the 1CBF of the brain-stem begins to decrease. 2) Alterations in the 1CBF of the upper brain-stem at the beginning of uncal herniation. 3) Alterations in the 1CBF of the medulla oblongata during the Cushing response. Using 40 cats, platinum electrodes were placed stereotaxically in the thalamus (Th), inferior colliculus (IC), and medulla oblongata (MO) for measurement of 1CBF by the hydrogen clearance method. The 1CBF of the brain-stem was serially measured before and after intermittent increase in ICP produced by inflation of an extradural balloon. Arterial blood pressure and supra and infratentorial extradural pressures were continuously recorded. The mean control 1CBF in the Th, IC, and MO were 37.5±9.9, 42.1±8.6, and 30.7±4.9 ml/100 g/min, respectively. At 20 to 30mmHg of supratentorial pressure (STP), the 1CBF of the Th started to decrease, and at 20 to 30mmHg of infratentorial pressure (ITP), the 1CBF of the IC started to decrease. Finally, at 40 to 60mmHg of ITP, the 1CBF of the MO was affected. At the beginning of the uncal herniation suggested by anisocoria, the mean 1CBF of the IC abruptly decreased from 33.7 to 19.6 ml/100 g/min (n = 16). In this stage, the pressure gradient between the supra and infratentorial spaces was 24.6±11.4mmHg. The Cushing response was evoked at STP 93.4±14.6mmHg and ITP of 49.9±6.8mmHg (n=16). The blood pressure significantly increased from 121.5 to 140.OmmHg. However, immediately before and during vasopressor response, little change was noted in the mean cerebral perfusion pressure (CPP) of the posterior fossa, i.e., from 89.0 to 89.6mmHg. The 1CBF of the MO did not show significant change either, i.e., from 22.8 to 20.9 ml/100 g/min. The data suggested that in supratentorial mass lesion, the 1CBF of the thalamus decreased first, followed by the 1CBF of the inferior colliculus, and then of the medulla oblongata. At the beginning of uncal herniation, the 1CBF of the upper brain-stem markedly decreased. During the Cushing response, the 1CBF of the MO did not change significantly.

Increased intracranial pressure and tentorial shear strain.

Tentorial herniation is caused by a pressure gradient between supra and infratentorial compartments and the herniated brain is burdened with a force, which is called shear strain at the edge of the tentorium. The purpose of the present study is to clarify the relationships between increased intracranial pressure, the pressure gradient and the tentorial shear strain. Twenty-three monkeys were used and intracranial pressure was raised by inflation of an epidural balloon placed in the right temporal region. The supratentorial pressure was found to be always higher than the infratentorial pressure and the pressure gradient became greater as intracranial pressure increased. The shear strain at the tentorial edge began to develop as soon as the balloon was expanded, and showed a slow and steady increase even when the intracranial pressure was only slightly increased and the pressure gradient did not have any effect. The degree of the tentorial edge descent observed by X-ray was, however, variable depending upon the animals used. The tentorial edge ceased to descend at the moment the tentorial shear strain was 80-140 mm Hg. At this point and thereafter, the characteristics of both herniated brain and tentorial edge changed from elastic to plastic, and the damage caused by the strained tentorial edge is thought to be tremendously extensive. Our dynamical study of transtentorial herniation shows clearly that the magnitude of shear strain was greater as a local forced pressure than supra and infratentorial pressure.

Experimental brain death. I. Morphology and fine structure of the brain.

The morphological characteristics of brain death were examined in baboons and cats after artificial cerebral ischaemia. All animals showed autolytic changes in the brain, ischaemic neuronal changes, midbrain haemorrhages, focal necrosis of the brain-stem, demarcation at C 1/C 2 cord segment, and displacement of cerebellar tissue. Ultrastructural examination revealed extreme brain oedema, autolytic changes, and complete obstruction of capillaries by astrocytic and endothelial swelling and intravascular blebs. These data indicate that brain death develops in several stages. If the process starts in the supratentorial space it first leads to a breakdown of the cerebral circulation and to transtentorial herniation. As a result, midbrain haemorrhages develop and the infratentorial pressure begins to rise. The second stage is terminated by demarcation of the brain. The circulatory arrest is initially caused by venous compression but becomes irreversible when vascular obstruction develops.

The effects of mass-induced intracranial pressures on arterial hypertension and survival in awake cats.

✓ Intracranial pressures above and below the tentorium, arterial blood pressure, heart rate, and respiratory rate were recorded continuously before, during, and after expansion of a supratentorial mass in awake unsedated cats. In general, as the mass enlarged, the intracranial pressure rose; however, considerable variation was observed among animals with respect to specific mass size and associated intracranial pressures. There was considerable variation in the relationship of supratentorial pressure to infratentorial pressure. No animal survived that had sustained a mass-induced pressure exceeding 1100 mm H2O, and survival was shorter with greater pressures. Systemic hypertension occurred always and only when the infratentorial pressure exceeded 600 mm H2O, regardless of the magnitude of the associated supratentorial intracranial pressure. The methodological limitations of previous studies of mass-induced intracranial hypertension appear to have been substantially reduced by the technique described.