TREATMENT OF OBSTRUCTIVE HYDROCEPHALUS BY PUNCTURE OF THE LAMINA TERMINALIS AND FLOOR OF THE THIRD VENTRICLE JOHN E. SCARFF, M.D. Department of Neurological Surgery, College of Physicians and Surgeons, Columbia University; and the Service of Neurological Surgery, Neurological I~tstitute of New York, Columbia-Presbyterian Medical Cerder, New York (Receivedfor publication September1, 1950) 'VMEROUS procedures have been devised over the years to relieve ob- structive hydrocephalus by diverting the cerebrospinal fluid from the N obstructed ventricles into tissue spaces or systems unsuited to the natural disposal of this fluid, such as the subdural space, the subgaleal space, the peritoneal cavity, or the genito-urinary system. The principle that it is necessary to drain the cerebrospinal fluid from the obstructed ventricles into the subarachnoid space, whence it can be removed by natural physiologic mechanisms, was first stated by Dandy. In 19~, 1 he described an operation for establishing communication between the third ventricle and the cisterna interpeduncularis. Dandy approached the chiasm through a small frontal flap, divided the optic nerve, elevated the optic chiasm and tract, and made a puncture into the hypothalamic por- tion of the third ventricle. He performed this operation on 6 patients but gave no case reports and made no claim for its success. He subsequently modified his technique to avoid dividing the optic nerve; this he did by ap- proaching the hypothalamus through a temporal flap and along the floor of the middle fossa. There are no case reports of this operation by Dandy. In 1936, Stookey and the present writer3 reported a different method for third ventriculostomy, which they described as "puncture of the lamina terminalis and floor of the third ventricle." The technique of this operation is here given. TECHNIQUE A coronal incision is made, following which a small right frontal osteoplastic. flap is turned up. This is carried down as low onto the brow as the frontal sinus will permit, and directly to the midline. A dural flap is then reflected toward the midline. The lateral ventricle is tapped to relieve pressure, following which the frontal lobe is retracted from the floor of the frontal foss/L to expose the optic chiasm and peri- chiasmal region (Fig. 1). The optic chiasm in hydrocephalus lies close to the tuber- culum sellae. A thin arachnoid membrane stretches upward from the superior surface of the chiasm to the under surface of the frontal lobes, hnmediately behind this membrane lies the cisterna chiasmatis, the posterior wall of which is the lamina terminalis. In typical cases of hydrocephalus, the lamina terminalis is seen as a bulg- ing membrane about 1-1.5 cm. in diameter, which appears dark blue. The membrane is quite thin, and its apparent color is due to light reflected back from fluid within the distended third ventricle. A small incision is made through the arachnoid mem- 204 TREATMENT OF OBSTRUCTIVE HYDROCEPHALUS ~05

FXG. 1. Anatomical structures involved in puncture of lamina terminalis and floor of third ventricle. The anterior wall of the cisterna chiasmatis is formed by an arachnoid membrane, while the posterior wall is the lamina terminalis itself. The attenuated floor of the third ventricle forms the anterior boundary of the cisterna interpeduncularis. The arrows indicate the points at which communication is established by the operation between the third ventricle and the two cisternae. (Drawing reproduced from original description of operation. 3)

FIG. 2. Technique of puncture of lamina terminalis and floor of third ventricle. (A) The anterior arachnoid walls of the cisterna chiasmatis and the lamina terminalis have been incised, and a dental instrument has been introduced through these incisions into the third ventricle until its tip is brought into contact with the dorsum sellae. (B) The tip of the dental instrument, guided entirely by sense of touch, has been gradually made to "walk up" the inner wall of the dorsum sellae until the tip rests on the lip of the dorsum. (C) The tip of the instrument has been advanced over the lip of the dorsum sellae, tearing a rent in the paper-thin floor of the third ventricle, and thus establishing communication between the ventricle and the interpeduncular cistern.