The perineurial vessel: a possible candidate for the structural basis of the meridian (Jing-Luo) in Chinese medicine.

A new concept is proposed of the 'perineurial vessel' as another vascular system of the body. The effects of acupuncture and moxibustion are explained as mechanical or thermal stimulation of intraperineurial cerebrospinal fluid (CSF). Fenestrated venous capillaries of circumventricular organs, including the choroid plexus, instead of arachnoid granulations, are shown to be the main site of CSF absorption. A new concept is also presented of a double circulatory system of the body, namely, in addition to the cardiovascular system, a lympho-liquid system with complete fluid circulation throughout the entire body.

Characteristics of distribution and configuration of intracranial arachnoid membranes.

An understanding of the microsurgical anatomy of the arachnoid membranes and the subarachnoid cisterns is important in minimally invasive neurosurgery. But the topography of the arachnoid membranes has not been completely elucidated. The description of the distribution and the configuration of the intracranial arachnoid membranes is still a subject of controversy. In order to clarify this we examined eight Han Chinese adult human cadavers under an operating microscope. The dissections were performed with microsurgical instruments and techniques without staining of the intracranial structures nor injection of colored material into blood vessels. Twenty seven arachnoid membranes were identified. They were named according to their locations and attachment. They were divided into three groups: basal, convex and trabecular arachnoid membranes. They varied greatly in appearances and configurations. They were single-leaf structured except Liliequist's membrane, the chiasmatic membrane and the cerebellar precentral membrane. They were distributed extensively and unevenly and crisscrossed in the cranial cavity. The more complexly and intricately the blood vessels or the nerves converged or branched within the subarachnoid space, the more luxuriant and complex the arachnoid membranes and trabeculae were. The areas where the arachnoid membranes crowded most thickly in the subarachnoid space included the regions around the bifurcation of the internal carotid artery, the area around the hypothalamus, the interpeduncular cistern, the arachnoidal sheaths of the oculomotor nerve, the quadrigeminal cistern and the cisterna magna. Almost all the cranial nerves were encased by their own arachnoidal sheaths when they crossed the cisterns. The arachnoid membranes and trabeculae must be dissected or incised sharply during the operations. Thorough knowledge of the anatomy of the intracranial arachnoid membranes is valuable to take full advantage of the natural anatomic landmarks and interfaces formed by them during surgery.

Microsurgical anatomy of Liliequist's membrane.

OBJECTIVE: To investigate the anatomic characteristics of Liliequist's membrane. METHODS: Liliequist's membrane was studied in eight adult human cadavers under the microscope. RESULTS: Liliequist's membrane gives rise to three separate arachnoidal sheets: the diencephalic leaf, the mesencephalic leaf, the diencephalic-mesencephalic leaf. The superior margin of the diencephalic leaf between the inferolateral border of the optic tracts and the temporal unci is free. The posterior margin of the diencephalic-mesencephalic leaf is free. The diencephalic leaf and the mesencephalic leaf attach laterally to the mesial temporal surfaces. Liliequist's membrane attaches closely to the hypothalamus. The diencephalic leaf is an accurate landmark which divides the cisterns of the skull base into two groups: pre-Liliequist group and post-Liliequist group. Liliequist's membrane should be opened sharply in order to avoid the injuries to the hypothalamus by blunt operations. In a pterion approach the diencephalic leaf of Liliequist's membrane can be determined according to the relationship with the posterior communicating artery. CONCLUSIONS: Liliequist's membrane is an important landmark for the operations in the sellar area or skull base. Understanding the microanatomy of Liliequist's membrane may be helpful for us to improve the exposure and minimize the injuries during the operations.

The arachnoid and the myth of Arachne.

The discovery of the arachnoid membrane is a relatively recent advance. Ancient anatomists noted the presence of the dura mater and pia mater, but the intervening arachnoid membrane was left undescribed. It was not until the 17th century that anatomists discovered a layer separating the pia mater from the dura mater and named this cobweb-like layer the "arachnoid." Arachnoid means "spider-like" and has an interesting etymology that can be traced to the ancient Greek myth of Arachne.

Discovery of the arachnoid membrane.

The history of the arachnoid membrane from antiquity to the present time is presented, including its anatomy, histology, and role in the absorption of cerebrospinal fluid. Special regard is given to the pioneering work of Key and Retzius.