GANGLIFORM ENLARGEMENT ON THE LATERAL CUTANEOUS OF THE ITS SIGNIFICANCE IN THE UNDERSTANDING OF THE ETIOLOGY OF MERALGIA PARESTHETICA HILEL NATHAN, M.D.* Department of Anatomy, The Hebrew University-Hadassah Medical School, Jerusalem, Israel (Received for publication July 18, 1959) ANGLIFORM enlargements ("pseudoganglions") have been de- scribed 3,6,9,1~ at or near the termination of various of the G body such as the median nerve, the anterior tibial (deep peroneal) nerve, the nerve to the teres minor muscle, and the posterior interosseous nerve. In the present study a similar enlargement will be described as found frequently on the lateral cutaneous nerve of the thigh. Its existence is not mentioned in current textbooks or other anatomical literature and its pres- ence may throw some light on the etiology of meralgia paresthetica. MATERIAL The present work is based on 60 dissections of the lateral cutaneous nerve of the thigh in cadavers. DESCRIPTION In 10 (17 per cent) of the specimens, a fusiform swelling of the lateral cutaneous nerve of the thigh was found (Fig. 1). In ~6 (43 per cent) a progressive, nonfusiform, broadening of the ter- minal part of the nerve was observed (Fig. r In the remaining ~4 cases (40 per cent) there was no substantial change in width of the nerve along the whole length of its course. When the gangliform enlargement was spindle-shaped (Fig. 1), it was generally localized in the part of the nerve passing beneath the (Poupart's ligament); at that point the nerve describes a more or less acute angle open downwards and posteriorly (Fig. 3). This angulation comes about as consequence of a change in the direction of the nerve when passing from the to the thigh. In the beginning of its course, after appearing from under the lateral border of the psoas muscle, the nerve runs laterally downwards, and forwards, included in the iliac ; 23 before reaching the inguinal ligament, it becomes more horizontal or even ascends slightly. When crossing the inguinal ligament, the nerve sharply changes its direction to run downwards and, sometimes, slightly posteriorly. Starting slightly proxinlal to the inguinal ligament and ending somewhat distal to it, * Formerly Hilel Notkovieh. 8~3 844 HILEL NATHAN the swelling occupied the apex of the angle; and it lay on the iliac muscle, on the proximal part of the sartorious and on a fibrous tissue between these two muscles. The inguinal ligament does not appear to compress the nerve at this point. It varied in length between 15 and 30 mm. ; in breadth it varied between 8 and 8 mm., while the original width of the same nerve, as it emerged from the lateral border oF the psoas muscle (Figs. 1 and ~), was

FIG. 1. Gangliform enlargement of lateral cutaneous nerve of the thigh. The enlargement is spindle- shaped, and localized in that part of the nerve passing from the pelvis to the thigh, just in front of the anterosuperior iliac spine. The nerve and swelling have been slightly raised by means of forceps. 1.c.n.--lateral cutaneous nerve of thigh; g.e.--gangliform enlargement; i.m.--; p.m.-- ; p.m.m.--psoas minor muscle; s.m.--sartorius; s.i.a.--anterosuperior iliac spine; c.i.--iliac crest; c.o.m.--aponettrosis of external oblique muscle, reflected downwards.

only 0.5 to ~ mm. In ~ cases the nerves did not pass under the inguinal liga- ment but crossed over the iliac crest, perforating the , slightly posterior to the anterior iliac spine; in both these cases angulation of the nerve was very sharp and its fusiform swelling was very evident.