Value of brainstem acoustic evoked potentials in posterior fossa tumours in childhood.

Brainstem acoustic evoked potentials (BAEPs) were measured in 14 children with different type of posterior fossa tumours several times during the clinical course, in order to assess the value of this simple and non-invasive method in the diagnosis and follow-up of posterior fossa tumours in childhood. Eight children had midline medulloblastoma, three children had lateral astrocytoma, three had intrinsic brainstem glioma. Different BAEP patterns could be detected in different tumour's type: bilateral symmetrical or slightly asymmetrical I-V. IPL prolongation in midline medulloblastomas, unilateral or markedly asymmetrical I.-V. IPL prolongation or wave V. depression on the contralateral side in lateral astrocytomas, and severely distorted asymmetrical waveform in intrinsic brainstem gliomas. The BAEPs were abnormal earlier than CT scan in a case of craniospinal astrocytoma. BAEPs were useful in the follow-up: the effect of the preoperative chemotherapy or the progression of the inoperable tumours could be as well documented by this method, as by the CT scan. BAEPs proved effective in the assessment of postoperative neurological complications: bilateral symmetrical IPL prolongation and wave V. depression with clinical signs of increased intracranial pressure occurred in a case of postoperative occlusive hydrocephalus, unilateral IPL prolongation occurred during irradiation or chemotherapy after medulloblastoma removal as signs of cerebral oedema.

[Brainstem acoustic evoked potential (BEAP] in children with posterior fossa tumors]. / Agytörzsi acusticus kiváltott potenciál (BAEP) vizsgálatok értéke gyermekkori hátsó scala tumorokban.

Brainstem acoustic evoked potentials (BAEPs) were recorded in 16 children with posterior fossa tumours. The results were compared with the clinical course, CT scan findings and the postmortem pathological findings. Eight children had midline medulloblastoma, four children had lateral astrocytoma (two of them cerebellar, one of them pontocerebellar, and one of them craniospinal) and four children had brainstem glioma. Different BAEP pattern could be detected according to the tumour's location and histological nature: 1. In midline medulloblastoma: bilateral, symmetrical, or slightly asymmetrical I-V. IPL prolongation was the common abnormality. Beside that, some of the patients showed III-V., or I-III. IPL prolongation, or V. depression. 2. In lateral astrocytoma: asymmetrical BAEP abnormalities were seen: unilateral V. depression, and/or I-V. IPL prolongation. 3. In brainstem glioma: severely distorted waveform could be observed, with depression and gradual disappearance of components following the wave III. Based on these results BAEP measurement seems to be useful in the differential diagnosis of posterior fossa tumours of childhood, and it can be necessary even beside the CT scan. It can be useful in the early diagnosis, because the BAEP positivity can precede the CT scan positivity, in such a case repeated CT scan required. Finally BAEP measurement proved to be effective in the follow-up of posterior fossa tumours: it can document the tumour's chemotherapeutic regression, or the progression. It is a simple, non-invasive, and cheap method.

Cochlear blood flow during stepwise bleeding and CO2 inhalation in the anaesthetized dog and cat.

Normal blood flow values, autoregulatory tendency and CO2 sensitivity of the cochlear blood vessels were studied in acute experiments in anesthetized, artificially ventilated dogs and cats. Cochlear blood flow was measured with the hydrogen-gas clearance technique using 100 mu platinum electrodes implanted into the perilymphatic space. Normal mean cochlear blood flow at normal systemic blood pressure and arterial pH values was found to be 30 +/- 7 ml . 100 g-1 . min-1 in the dog, and 16 +/- 5 ml . 100 g-1 . min-1 in the cat. There was no evidence of the existence of an autoregulatory mechanism of cochlear blood flow during stepwise bleeding in the dog. Blood flow seemed to follow passively the changes of arterial pressure. Cochlear blood flow increased by 79% on 5% CO2 inhalation in the cat, as a result of decreased vascular resistance. The relationship between arterial pCO2 values and cochlear blood flow proved to be exponential.

Ultrastructural organization of the round window membrane in the infant human middle ear.

Ultrastructural studies of the round window membrane in infants revealed that the membrane is made up of three layers. The relatively wide outer epithelial layer consists of 3-4 cell layers and is formed by cuboidal and round cells. The outer two or three cell layers contain mainly rough endoplasmic reticulum and secretory granules, indicative of a secretory function of the epithelial cell layer of middle ear mucosa. Tonofilaments occur mainly in the more electron-dense epithelial cell layers which makes their mechanical role more probable. The connective tissue layer is relatively narrow and contains fibrocytes, much collagen and relatively few elastic fibres. The inner epithelial layer is built up of elongated cells containing rough endoplasmic reticulum cisternae in their cytoplasm.

Experimental round window membrane rupture.

An increase of perilymphatic fluid pressure was found to be an important factor in the aetiology of round window membrane rupture. The critical pressure causing membrane rupture, as determined in anaesthetized cats, was in the range of 10-30 mm Hg (mean, 23.4 +/- 17.1). This value was compared to the pressure increases caused by thoracic and abdominal compression, cervical strangulation, forced Trendelenburg position, coughing, and sneezing.

Investigations on the critical perilymphatic pressure value causing round window membrane rupture in anesthetized cats.

Increasing perilymphatic fluid pressure was found to be an important factor in the etiology of round window membrane rupture. The critical pressure, causing membrane rupture was determined in anesthetized cats. Its value was found to be in the range 10--30 mmHg (x+/-S.E.M.=23.4+/-17.1). This value was compared with the pressure increases caused by thoracic and abdominal compression, cervical strangulation, forced Trendelenburg position, coughing and sneezing.

The ultrastructure of the round window membrane of the cat.

The ultrastructure of the round window membrane of the cat was investigated. Three distinct layers were recognised and described. It was established that the outer epithelial layer is non-ciliated, but often contains microvilli. The middle layer, under the basement membrane, contains a large amount of collagen and elastic fibres in addition to fibrocytes. The inner layer is a continuation of the epithelial layer of the perilymphatic space. The thickness of the membrane has been measured as being 15--20 micrometer. The latest human audiological and clinical observations concerning the function and rupture of the round window membrane emhasise the importance of the electron microscopic study of this membrane.

[Hearing- and vestibular functions after neonatal hyperbilirubinaemia (author's transl)]. / Untersuchungen der Gehör- und Vestibularfunktion nach Icterus gravis

Cochlear- and vestibular function were investigated in 72 patients, aged between 4 and 7 years who had neonatal hyperbilirubinaemia. Markedly more and more serious damage was found in the group of patients, who as neonates had serum bilirubin levels above 25 mg-%. The frequency of loss of cochlear and vestibular function was significantly higher in patients with hyperbilirubinaemia for more than 4 days. Contrary to data published until now, it can be concluded that the vestibular apparatus is the most sensitive part of the nervous system to bilirubin.