Anatomic variants of the cerebello-pontine cisterns and their significance in positive contrast cisternography

Far lateral extension of the cerebello-pontine cistern is a common variant which is found in greater than 50% of people. When present it may cause the internal auditory canal to be obscured during positive contrast cisternography. A technique of cisternography is described which facilitates the diagnosis of intracanalicular lesions as well as better delineating small lesions in the cerebello-pontine angle.

The structure of the rhombencephalic roof in the frog

The structure of the rhombencephalic roof has been studied by serial section histology in 12 adult frogs, 3 recently metamorphosed frogs and 8 tadpoles of the species Rana temporaria. The roof of the rhombencephalon caudal to the choroid plexus consists of a delicate layer of ependyma which appears to be intact from the time of its development in the tadpole until the stage of metamorphosis. In the adult frog it is an attenuated structure displaying variable deficiencies with an apparent communication between the rhombencephalic ventricle and the surrounding subarachnoid space. The significance of this acquired communication between internal and external cerebrospinal fluid compartments in the adult frog is discussed in relationship to the classical concepts of bulk flow of the CSF in humans. Some of the limitations of these classical concepts are also discussed, and the approach to these problems by studying the comparative morphology of the CSF system in vertebrate animals is justified.

Anatomical observations of the subarachnoid cisterns of the brain during surgery

Subarachnoid cisterns and their contents are described briefly in the light of observations made during microsurgical explorations. The concept of intracranial surgery in terms of moving from one cistern to another is presented here with particular emphasis on the cisterns in surgical approaches to intracranial vessels and nerves for the treatment of aneurysms, arteriovenous malformations, and for surgery of basal tumors.

Further studies on the difference between ventricular and subarachnoid perfusion

In order to study the exchanges between the subarachnoid fluid and the adjacent cortical tissue independently of the choroid plexus, artificial cerebrospinal fluid (CSF) was perfused from the supracallosal cistern to the cisterna magna in the rabbit. Test substances were introduced into the blood and held at a constant level. The degree of penetration by the blood-borne test substances into the artificial CSF perfused into the cortical subarachnoid space was noted. The degree of penetration of these test substances into the artificial CSF does not solely reflect rates of exchange between this fluid and the exposed cortex for it was shown histologically as well as physiologically that the artificial CSF does not remain in the subarachnoid space but also enters the subdural space to exchange with the blood via the dural capillaries. Thus this experimental model routinely produces an artefactual situation which restricts its use in the study of CSF-brain relations.

Developmental morphology of the subarachnoid space and contiguous structures in the mouse

Development of pia-arachnoidal membranes in the mouse occurs in four stages: the first (prenatal days 10-13) follows closure of the neural tube and is a period of initial vascularization of the developing telencephalon; the second (prenatal days 14-16) is a period of delineation during which the limits of the subarachnoid space are defined; the third (prenatal day 17 to birth) is a period of ensheathment of pia-arachnoidal blood vessels; and the fourth (birth to postnatal day 21) includes addition of smooth muscle to larger vessels, the appearance of macrophages in the subarachnoid space, and a general increase in extracellular collagenous and elastic fibers. The mesenchyme over the telencephalic surface in the 10-day fetus has a typically large extracellular space. By the 13th fetal day cerebrospinal fluid begins to seep into and replace it. The mesenchymal extracellular compartment is reduced peripherally, resulting in a compacted pia-arachnoidal tissue which limits the peripheral extent of the subarachnoid space. By the 21st postnatal day a subarachnoid space typical of the adult animal has been established.

Mechanisms of cervical nerve root avulsion in injuries of the neck and shoulder

✓ The author reviews the mechanisms of traumatic spinal nerve root avulsion and proposes a new interpretation.

Structure of the human arachnoid granulation

✓ The human arachnoid granulation was studied by light microscopy in gapless serial sections after local postmortem perfusion of the subarachnoid space with glutaraldehyde. The smaller granulations are invested in a dural sheath several layers thick which is separated from the body of the granulation by a true subdural space. In larger granulations, there are restricted regions where the body of the granulation protrudes through the dura to enter the venous sinus directly.

Special features of the rabbit cerebroventricular system, studied by the casting method

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