The efferent projections of the fornix system have been studied in the squirrel monkey using modified silver staining techniques to delineate degP*.mating fibers and terminal boutons after inducing careful lesions of the subcallosal fornix and dorsal fornix.Subcallosal fornix projections, after supplying the medial and lateral septa1 nuclei, are traced via precommissural fibers to terminal degeneration in the nu&us of the diagonal band of Broca, nucleus accumbens, ~Y N S rectus, olfactory tubercle, medial and lateral preoptic areas, and medial hypothalamus. Degenerating precommissural subcallosal fornix fibers course with the medial forebrain bundle throughout the extent of the lateral hypothalamus, extending caudally to the medial mammillary nucleus with specific hypothalamic offsets to the tuberal region and nucleus intercalatus (''lateral cortico-hypothalamic tract"). Subcallosal postcommissural fornix fibers are traced to terminal degeneration in the bed nucleus of the stria terminalis and medial preoptic and anterior hypothalamic structures (''medial cortico-hypothalamic tract"); fornix column fibers disperse throughout the perifornical nucleus; these fibers more caudally supply nucleus intercalatus and medial mammillary nucleus. In the thalamus postcommissural fibers supply the nucleus reuniens, the paraventricular, anterior ventral, and lateral dorsal nuclei. In the mammillary nucleus a laminated radiation is described with some fibers extending caudally to the prerubral field.A "midline subcallosal stria," derived from the subcallosal fornices, distributes fibers to the subfornical organ, the dorsal part of the medial septum, the precommissural fornix and especially the medial cortico-hypothalamic tract.The dorsal fornix projection is predominantly pericallpsal to the ~Y N S rectus and parolfactory area, with only a minor callosal-penetrating contribution to pre-and postcommissural fibers.The composite projections of the hippocampal formation fornix system appear more extensive than those of the amygdala to basal forebrain, preoptic, and hypothalamic areas.A review of anatomical descriptions of fornix system projections, comprising a voluminous literature, reveals significant discrepancies. Although G. Elliot Smith concluded in 1897 that I'. . . the fornix conforms to one and the same fundamental plan in the arrangement of its fibers in all vertebrates," five years later Edinger and Wallenberg ('02) found that postmammillary fornix connections differed significantly in different strains of rabbits. Thereafter, many of the seeming discrepancies of the early studies were explained by further work which showed that there is significant interspecific variability in the distribution and extent of direct fornix fibers (Tello, '36; Simpson, '52; Cowan and Powell, '55; Valenstein and Nauta, '59).Recently further clarification of fornix system projections has been achieved using the newer technique of studying axonal transport CHARLES E. POLETTI AND GEORGE CRESWELLof radioactive amino acids (Swanson and...

Two cases of progressive, occipital lancinating pain and dysesthesias associated with a sensory deficit of the C2 dermatome are presented. Symptoms were relieved, and C2 sensory function restored by releasing a hypertrophied atlanto-epistrophic ligament entrapping the C2 root and ganglion. The normal anatomy and abnormal surgical findings are described. C2 entrapment by the atlanto-epistrophic ligament is discussed in reference to other C2 lesions causing occipital pain. We conclude that some patients whose progressive occipital pain is accompanied by a C2 sensory deficit are suffering from entrapment of the C2 root and ganglion amenable to surgical decompression.

Two patients with spontaneous spinal subarachnoid hemorrhage are presented to emphasize the clinical and radiological features of this uncommon illness. Both had severe back pain at the onset. One patient had a subdural hematoma that compressed the conus medullaris and cauda equina, and was drained percutaneously; the other had clots in the subarachnoid space. The cerebrospinal fluid showed a polymorphonuclear pleocytosis that simulated septic meningitis. Complete spinal angiography failed to reveal a cause for the hemorrhages.

No abstract