The role of the lymphatic system in drainage of cerebrospinal fluid and aqueous humour.

Abstract

SUMMARY1. The jugular lymphatic trunks were cannulated in anaesthetized rabbits and cats.Over 6-8 hr, the mean lymph flow was 2-3 gl. min-in the rabbit (one side only) and .5-0 ,sl. minm-in the cat (sum of both sides).2. After a single injection of radio-iodinated albumin into a lateral cerebral ventricle without significant rise in pressure, a mean of 14-4 % of the radioactivity was recovered in deep cervical lymph of one side in the rabbit and of 12-9 % in that of both sides in the cat. 5. No significant radioactivity, other than from blood, was detected in deep cervical lymph of the rabbit or in deep and superficial cervical lymph of the cat within 6 hr after injection of radio-iodinated albumin into the aqueous humour or orbital fat.6. Gradients of radioactivity in tissues within the orbit suggested that there is a small flow of c.s.f., 0-05-0-15 /t.l min-' in the rabbit, passing centrifugally along the subarachnoid space of the optic nerve, through the posterior part of the globe and into the orbital tissue. Also a small proportion of aqueous humour, 1-2 % or more, drains through the anterior sclera into the surrounding tissue. 7. A substantial quantity of cerebrospinal fluid drains into the deep cervical lymphatic system of the rabbit, 30 % or more, and of the cat, 10-15 % or more. The small component of aqueous humour drainage passing through the wall of the glove does not enter cervical lymph within 6 hr, if at all.

A model to measure lymphatic drainage from the eye

“…It should be noted however, that there is some contradictory evidence. In rabbits and cats, no radioactivity was observed in the cervical lymph within 6 hours after injection of radioactive albumin into the aqueous humor (Bradbury and Cole, 1980). In addition, the expression of 5" nucleotidase (a putative lymphatic endothelial marker)…”

Orbital lymphatics: do they exist?

“…5 Furthermore, a number of authors have proposed that part in the cerebrospinal fluid outflow pathway involves the lymphatic system, and that such a system exists in the orbit. [6][7][8] In the context of the lymphatic identification problems already described, the issue as to whether orbital lymphatics exist continued to challenge researchers until very recently. Several approaches were taken in attempts to identify orbital lymphatic flow.…”

Communications

“…In rabbits anaesthetized with pentobarbitone, one jugular lymph trunk was cannulated and, after turning the animal to the prone position, cannulae screwed into both lateral ventricles (Bradbury & Cole, 1980 This rose to 5 5+0 4 and 9-1 +0-3 mmHg respectively at the two infusion rates. At normal pressure, the recovery of L125Ilalbumin in lymph (one side) over 6 hr was 14-8 + 13 00 (S.E., n = 12).…”

“…Mellor & Slater (1971) (Brierley & Field, 1948). Compounds of large molecular weight were recovered from deep cervical lymph after intraventricular injection (Bradbury & Cole, 1980). The effect of pressure on the fraction of cerebrospinal fluid (c.s.f.)…”