Meningeal Carcinomatosis

Meningeal carcinomatosis without gross tumour in the substance of the brain or spinal cord has been reported rarely. Two cases observed at the Victoria General Hospital, Halifax, presented a bizarre clinical picture consisting of signs of meningeal irritation without fever, and psychotic behaviour. Examination of the cerebrospinal fluid revealed low sugar concentration and increased pressure, protein and cells. In one case these cells were readily identified as malignant on stained smears. At autopsy the surfaces of the cerebral hemispheres, cerebellum and brain stem were covered by an opalescent film and on section the subarachnoid space was densely packed with malignant cells. Both primary tumours were adenocarcinomas, one originating in the gallbladder and one in the rectum. The diagnosis of meningeal carcinomatosis must be considered in patients presenting with profound mental changes and meningeal irritation without fever. Diagnosis may be confirmed by cytological examination of the cerebrospinal fluid. The primary tumour is most commonly an adenocarcinoma. There is no satisfactory treatment available.     

Carcinomatosis of the Meninges

Some clinical and pathological features of carcinomatosis of the meninges are reviewed along with a report of four cases. This condition usually presents in middle age as a subacute meningitis with cranial nerve involvement, but the diagnostic importance of the various mental disturbances which may be encountered early in its course are noted. The acute or subacute course may reflect a widespread mechanical interference with normal cerebral metabolism, a notion which is supported by recent clinical measurements in these patients of the rate of glucose transport across the blood-brain barrier. It is probable that the route taken by tumour cells to reach the meningeal spaces is a relatively unimportant factor in determining this pattern of growth and that the intrinsic growth characteristics of the primary tumour, its nutritional needs, and gravity probably play the major roles in production of this unusual type of secondary invasion. Greater therapeutic use of irradiation for these patients is encouraged.     

Meningeal worm in free-ranging deer in Nebraska

The meningeal worm (Parelaphostrongylus tenuis) was found in 22 (7%) of 300 white-tailed deer (Odocoileus virginianus) (257 adults, 43 fawns) examined from Nebraska (USA) during November 1996. None of 53 mule deer (Odocoileus hemionus) (47 adults and 6 fawns) examined were infected. Twenty-two white-tailed deer from 18 counties in eastern Nebraska were infected with Parelaphostrongylus tenuis. This is the first record of P. tenuis in white-tailed deer from this state.     

Meningeal worm in deer from western Nebraska

One hundred seventy-eight white-tailed deer (Odocoileus virginianus) and 275 mule deer (Odocoileus hemionus) collected from locker plants in the western 2/3 of Nebraska (USA) in November 1997 were examined for the meningeal worm (Parelaphostrongylus tenuis). Parelaphostrongylus tenuis was identified in 17 (10%) of 168 white-tailed deer and in one (<1%) of 273 mule deer. This is the first naturally occurring infection of P. tenuis recorded in a mule deer.     

Hypophysial and Meningeal Melanocytes in the Zucker Rat

Melanocytes have not been described in the pituitary of mammals or in the meninges of the rat. In this paper, we report the presence of the cluster of melanocytes in the intermediate lobe of the pituitary and around the median eminence of the hypothalamus forming an ‘infundibulo-hypophysial circle’, and also describe the characteristics of meningeal melanocytes in Zucker rats. In the leptomeninges, numerous melanocytes were found on the ventrolateral surface of cerebral hemisphere in the area of the middle cerebral artery. Pigment granules were also observed in the surrounding tissue outside the melanocytes as well as incorporated in the cytoplasm of neural and epithelial cells. Electron microscopy revealed that melanosomes in hypophysial and meningeal melanocytes were in different (II-IV) stages of maturity. In the leptomeninges of Zucker rats, HMB-45 immunoreactivity was found in round non-melanosome-containing cells, while no HMB-45 reaction was found in the leptomeninges of the albino rat. We conclude that both obese and lean Zucker rats possess functionally active melanocytes in the meninges and the pituitary and transfer pigment granules to neighboring cells. The distributions of melanocytes in proximity to blood vessels in the leptomeninges and in the ‘infundibulo-hypophysial circle’ suggest an endocrine secretory function.     

Photoimmunotherapy of Gastric Cancer Peritoneal Carcinomatosis in a Mouse Model

Photoimmunotherapy (PIT) is a new cancer treatment that combines the specificity of antibodies for targeting tumors with the toxicity induced by photosensitizers after exposure to near infrared (NIR) light. We performed PIT in a model of disseminated gastric cancer peritoneal carcinomatosis and monitored efficacy with in vivo GFP fluorescence imaging. In vitro and in vivo experiments were conducted with a HER2-expressing, GFP-expressing, gastric cancer cell line (N87-GFP). A conjugate comprised of a photosensitizer, IR-700, conjugated to trastuzumab (tra-IR700), followed by NIR light was used for PIT. In vitro PIT was evaluated by measuring cytotoxicity with dead staining and a decrease in GFP fluorescence. In vivo PIT was evaluated in a disseminated peritoneal carcinomatosis model and a flank xenograft using tumor volume measurements and GFP fluorescence intensity. In vivo anti-tumor effects of PIT were confirmed by significant reductions in tumor volume (at day 15, p<0.0001 vs. control) and GFP fluorescence intensity (flank model: at day 3, PIT treated vs. control p<0.01 and peritoneal disseminated model: at day 3 PIT treated vs. control, p<0.05). Cytotoxic effects in vitro were shown to be dependent on the light dose and caused necrotic cell rupture leading to GFP release and a decrease in fluorescence intensity in vitro. Thus, loss of GFP fluorescence served as a useful biomarker of cell necrosis after PIT.     

Meningeal worm in a reintroduced elk population in Kentucky

Meningeal worm (Parelaphostrongylus tenuis) has been implicated in the failure of several elk (Cervus elaphus) restoration attempts in the eastern United States. However, limited post-release monitoring and a paucity of published literature prevents a clear understanding of this parasite's role in past failures. During winters of 1997-2001, the Kentucky Department of Fish and Wildlife Resources translocated 1,044 elk from western states to eastern Kentucky (USA) in an effort to restore a free-ranging population. We monitored 521 radio-collared elk over 4 yr to determine the impact meningeal worm had on population establishment. Thirty (23%) of 129 non-capture related mortalities were attributed to meningeal worm. Twenty-two (73%) of these meningeal worm-caused mortalities were animals < 3 yr old. If younger elk born in Kentucky suffer higher mortality rates than older translocated elk, the population growth observed during the initial years of restoration may be temporary. Additional research is necessary to determine the influence meningeal worm will have on elk population growth in Kentucky.