Hydrocephalus: Historical Review

Hydrocephalus: Historical Review

Historical Summary and Future Perspectives

Although the history of hydrocephalus can be traced back to Hippocrates' description of external hydrocephalus, the prevailing humoral theory, later institutionalized as Galenism, hindered the recognition of internal hydroceph­ alus for nearly 2000 years.

Internal hydrocephalus was first recognized by Vesalius in 1543, after which a great deal of interest was focused on the anatomy of the cerebrospinal fluid (CSF) pathway. In the 18th century, Contugno (1764) and Haller (1768) gave fairly accurate accounts of the cerebrospinal fluid and Monro formulated a revolutionary theory on the nature of the intracranial volume (1783). In the 19th century, Magendie constructed a comprehensive picture of CSF circula­ tion (1842) and in 1875, Key and Retzius compiled a superb atlas of the CSF system. This, then, was "the third circulation" to be described, more than a century after the blood and lymphatic circulation systems had been established by Willis and Bartholin, respectively. The basis of modern research, therefore, was established in the fields of the physiology of CSF and the anatomy of its pathway.

With respect to pathology, with the exception of Morgagni 's description (1761) of the organ pathology of hydrocephalus related to myelomeningocele, only a little knowledge was gained until the mid-1900s, when tissue pathology was established. Until the 19th century, such congenital malformations were regarded as untreatable and high infant mortality was accepted as inevitable. The surgical implications of congenital malformations were first recognized in the late 19th century. The clinical entity of the Chiari malformation was established and arachnoid cysts and dysgenetic hydrocephalus, including the Dandy-Walker syndrome, holoprosencephaly, and hydroanencephaly were recognized.

Traditional medical treatment for hydrocephalus, which was essentially the same as that of the Hippocratic era, prevailed unt l the 18th century. In the early 1900s, the first new treatment, ventricular puncture, was attempted. This operation, based on the obstructive hypothesis, attempted a modification of the flow of the CSF. However, it was almost always fatal, despite the aid of newly invented listerism and ether anesthesia.

From the beginning of the 20th century until the 1950s, the aim of the many clinical and pathological studies was to demonstrate an anatomical obstruction to the major pathway of CSF. The concept of obstruction was formulated and published by Penfield and Elvidge (1932) and Russell (1942). Dandy and Blackfan's conclusion (1918) that CSF was derived mainly from the choroid plexus strongly influenced future surgical treatment. They developed and performed choroid plexectomy, third ventriculostomy and aqueductal canal­ ization. Their classification of hydrocephalus into communicating and non­ communicating types has since been used clinically without major modifications. Dandy developed the phenol-sulfonphthalein test, airencephalography, and airventriculography to diagnose communicating hydrocephalus. In the same era, Cushing proposed a distinguished theory on the biological role of CSF (1925), although until recently this theory could not be tested.

Although internal shunting had been attempted in the early 1900s, it was Nulsen and Spitz' work, in 1949, on the introduction of a one-way valve, which opened the modern era of treatment. Shunt procedures soon became widely accepted as an effective diversion method, which was regarded as bringing hydrocephalus to a surgically arrested state. At the same time, it was the beginning of an era of painful battles against shunt complications. Much effort was devoted to revising and upgrading the shunt system to a more physiological one with less risk of complications.

The introduction of radioactive tracers in the 1950s enabled the dynamics of the circulatory pattern of the CSF to be evaluated in detail. Since the 1960s, new research methods have updated earlier work. Papenheimer's perfusion method (1962), using various tracers, enabled not only the rate of formation and absorption at various pressure levels to be measured, but also contributed to the entire field of CSF physiology and pharmacology. With this method, the extrachoroidal formation of CSF was established. However, Katzman's infusion manometric test, developed in 1970, demonstrated various patterns of reduced absorption capacity or increased outflow resistance in hydrocephalus, which led to the concept of defective absorption.

Although useful data have been collected on the interaction of pharmaco­ logical agents on the formation of CSF, and on the pressure factors involved in its absorption, we have, as yet, no drugs available and no other more effective method than shunting.

The development of teratological induction methods and the introduction of hereditary models, established in the 1960s, enabled the pathology of congen­ ital hydrocephalus to be studied. These experimental studies were predicted to, and in fact did, provide data on the pathological cerebral changes which occur in hydrocephalus. Many experimental studies demonstrated secondary aqueductal stenosis; these findings were also supported clinically by Folz' reports of functional aqueductal stenosis which occurred after shunting, and by Raimondi's studies on Dandy-Walker cysts. Then Epstein proposed the existence of slit ventricle syndrome and the isolated fourth ventricle, which later led to the concept of isolation, or compartmentalization of the CSF space, which encompassed unilateral hydrocephalus and the isolated temporal horn. This concept emphasized the significance of the pressure differences between each isolated compartment in the pathogenesis of functional stenosis of the CSF pathway.

The description of normal pressure hydrocephalus by Adams and his col­leagues, in 1965, prompted and then advanced further research, especially on analysis of the correlation of intracranial pressure and pulse pressure with related physiological parameters and studies on biomechanics and their role in hydrocephalus.

Thereafter, as clinical experience with normal pressure, slowly progressive, and arrested hydrocephalus accumulated, insight was gained into these conditions. This led to the concept of chronological change in hydrocephalus, pro­ posed by Matsumoto in 1976. This concept proposes that hydrocephalus should be regarded as a dynamic process with a chronological sequence of events, which may be comparable to the life-cycle. Experimental studies with hered­ itary and teratologically induced models support the concept.

The interaction between CSF and cerebral extracellular fluid, originally suggested in the early 1900s, was further clarified. Ultrastructural studies defined the brain barrier systems, that is, the blood-brain, blood-CSF, and brain-CSF barriers. In 1965, Brightman and Reese demonstrated that the communication between cerebral extracellular fluid and CSF was relatively free. Milhorat (1970) showed that periventricular permeability was increased in experimental hydrocephalus. Later this was found to correlate with peri­ ventricular low density in X-ray CT and periventricular hyperintensity on MR­ CT. Cserr (1974) demonstrated the bulk flow of cerebral interstitial fluid, and Reulen (1977) demonstrated the bulk flow of edema fluid through the cerebral extracellular space. Thus, the accumulated data led to the concept of com­ pensation via transependymal and intraparenchymal absorption of CSF. If compensation is insufficient then the result is parenchymal damage. Thus, our attention was refocused on changes occurring in the brain in hydrocephalus.

In any era, the definition of hydrocephalus is a summary of the leading concepts of that era, based on each author's insights. Several definitions have been proposed in our era. In 1977, Raimondi classified intraparenchymal, extraparenchymal, and combined hydrocephalus according to their patho­ physiologies. In 1976, Matsumoto classified hydrocephalus based on changes in the flow dynamics of CSF, the degree of cerebral damage, and chronological change; he emphasized the necessity of considering changes in the cerebral parenchyma. At this stage, his new concept of dynamic changes and their chronological sequence in hydrocephalus was introduced. From its onset, hydrocephalus progresses, first, to the stage of pressure hydrocephalus, then through a normal pressure stage or, in some patients, slowly progressive hydrocephalus, and finally to the stage of arrested or compensated hydrocephalus with varying degrees of cerebral damage. This concept led to the definition of intractable hydrocephalus used by the Research Group of the Japanese Ministry of Health and Welfare.

Now, we are at a turning point in the history of hydrocephalus. Most of the 20th century was devoted to studying the altered physiology of CSF. As the 21st century approaches, the recognition of hydrocephalus as a brain disease should be reemphasized, which should lead to new treatment methods. Up­ dating of early work should be done with this in mind. Rapidly advancing technology, including positron emission CT, Magnetic Resonance Imaging, spectroscopy, and other sophisticated methods, should provide more advanced knowledge of the pathophysiology of the brain and should open a new era in the management of hydrocephalus. There is much promising data already. For instance, increased knowledge of nerve regeneration and remyelination may lead to drug therapy aimed at regrowth with functional recovery. The extravillous drainage mechanism, as represented by the supposed lymphatic route, and further clarification of the intraparenchymal absorption mechanism may lead to new methods which will reduce outflow resistance. Moreover, advanced research into the interaction of the brain-CSF interface should demand revision of diversion surgery to more physiological procedures which will allow the CSF to maintain its role as a biological fluid. Furthermore, in the near future, the concept of the isolated cerebrospinal fluid space, based on a pressure-difference mechanism, may prompt the invention of new treatments. We have already waited too long for the advent of more appropriate treat­ ments to replace shunting. Future treatment of hydrocephalus should be aimed at including effective functional recovery, and not simply at producing a surgi­ cally arrested state with brain damage.