Dandy-Walker-Like syndrome in a quarter horse colt.

A 6-hour-old Quarter Horse colt was examined because of an inability to rise. An uneventful parturition after a normal gestational length from a multiparous mare was reported by the owner. The colt was administered dexamethasone (4 mg) and gentamicin (400 mg) IV and mare’s colostrum (900 mL) PO before referral. Upon examination, the colt (59 kg) was depressed and recumbent. The rectal temperature was 97.6uF, heart rate was 110 beats/min, and the respiratory rate was 40 breaths/min The colt had a prominent domed forehead, but no other significant abnormalities were detected on physical examination. Hematologic and biochemical abnormalities were limited to an increased hematocrit (53%; reference range, 37– 49%), hypoproteinemia (4.3 g/dL; reference range, 5.1– 7.6 g/dL), and an increased serum creatine kinase activity (1597 U/L; reference range, 65–380 U/L). Results of the arterial blood gas analysis were normal. Initial treatment included fluids (500 mL 0.45% NaCl IV q2h), mannitol (1 g/kg IV q12h), amikacin (25 mg/kg IV q24h), ceftiofur (10 mg/kg IV q12h), equine plasma (1000 mL IV once), and feeding via a nasoesophageal tube (500 mL mare’s milk q2h). Disciplines Large or Food Animal and Equine Medicine | Veterinary Medicine | Veterinary Pathology and Pathobiology Comments This article is published as Wong, D., Winter, M., Haynes, J., Sponseller, B. and Schleining, J. (2007), DandyWalker-Like Syndrome in a Quarter Horse Colt. Journal of Veterinary Internal Medicine, 21: 1130–1134. doi: 10.1111/j.1939-1676.2007.tb03077.x . Posted with permission. Creative Commons License This work is licensed under a Creative Commons Attribution-Noncommercial 4.0 License This article is available at Iowa State University Digital Repository: http://lib.dr.iastate.edu/vpath_pubs/97 Dandy-Walker–Like Syndrome in a Quarter Horse Colt David Wong, Matthew Winter, Joseph Haynes, Brett Sponseller, and Jennifer Schleining A 6-hour-old Quarter Horse colt was examined because of an inability to rise. An uneventful parturition after a normal gestational length from a multiparous mare was reported by the owner. The colt was administered dexamethasone (4 mg) and gentamicin (400 mg) IV and mare’s colostrum (900 mL) PO before referral. Upon examination, the colt (59 kg) was depressed and recumbent. The rectal temperature was 97.6uF, heart rate was 110 beats/min, and the respiratory rate was 40 breaths/min The colt had a prominent domed forehead, but no other significant abnormalities were detected on physical examination. Hematologic and biochemical abnormalities were limited to an increased hematocrit (53%; reference range, 37– 49%), hypoproteinemia (4.3 g/dL; reference range, 5.1– 7.6 g/dL), and an increased serum creatine kinase activity (1597 U/L; reference range, 65–380 U/L). Results of the arterial blood gas analysis were normal. Initial treatment included fluids (500 mL 0.45% NaCl IV q2h), mannitol (1 g/kg IV q12h), amikacin (25 mg/kg IV q24h), ceftiofur (10 mg/kg IV q12h), equine plasma (1000 mL IV once), and feeding via a nasoesophageal tube (500 mL mare’s milk q2h). The colt became more alert and would struggle to rise intermittently over the next 12 hours and could briefly maintain a sternal position or stand when assisted. When standing, the colt would constantly sway his head and neck from side to side. Simultaneously, a pronounced truncal and hindquarter sway was observed in the same direction of head movements (See the video available online at http://dx.doi.org/10.1892/06-290v1). No abnormalities were noted for a foal of this age involving the cranial nerves, patellar reflex, triceps reflex, or withdrawl/flexor reflex. There was neither opisthotonus or intention tremors. Precise assessment of proprioception and postural reactions was not possible, because the colt could not stand or ambulate on his own. Based on neurologic examination, a lesion involving the cerebellum was suspected. On the second day of hospitalization, the colt was alert and would frequently struggle and make attempts to rise. There was a leukocytosis (13.50 3 10/mL; reference range, 4.9–11.7 3 10/mL) characterized by a neutrophilia (12.55 3 10/mL; reference range, 3.36– 9.57 3 10/mL); these changes could have been induced by stress, administration of steroids the day before or both. The serum immunoglobulin G concentration was greater than 800 mg/dL. A congenital malformation of the central nervous system (CNS) was suspected and computed tomography (CT) of the head was performed with the foal under general anesthesia. Transverse, contiguous 3-mm scans were obtained from the level of the frontal sinuses caudal to the first cervical vertebra. Studies were performed with and without administration of contrast (Hypaque 2 mL/kg IV). The 4th ventricle was markedly dilated, and, in the caudal fossa, dorsal to the rostral and caudal cerebellar peduncles in the region of the vermis, there was marked hypodensity (Figs 1 and 2). CT numbers in this location were consistent with (cerebrospinal fluid) (6–20), and markedly hypodense to the surrounding brain parenchyma (30–45). The lateral cerebellar hemispheres were considered normal, and there was no contrast enhancement. There were open sutures between the occipital and parietal bones, as well as the frontal and parietal bones, which were considered normal for a foal of this age. Findings were consistent with a hypoplastic vermis and ventriculomegaly of the 4th ventricle. The colt was euthanized, and a postmortem examination was performed. Relevant findings were limited to the brain and the skull. Aplasia of the cerebellar vermis was confirmed; the lateral cerebellar hemispheres were present but were separated by a gap where the vermis typically is positioned (Figs 3 and 4A). In addition, the lateral ventricles were mildly dilated. The foramina that connect the lateral ventricles to the third ventricle were dilated, as was the mesencephalic aqueduct. The 4th ventricle was dilated and covered by a thin roof of fibrous tissue, which was fused with the meninges, forming a meningocele (Fig 4A). The cisterna magna was expanded with cerebrospinal fluid, the corpus callosum was absent (Fig 4B), and the leptomeninges of the cerebral hemispheres were somewhat fused together along the longitudinal fissure. Furthermore, the gyri of the cerebral hemispheres were small, more numerous than normal, and somewhat convoluted (polymicrogyria). Microscopic findings of the cerebellar hemispheres consisted of dysplasia of the medial portions of the hemispheres that would normally be fused with the vermis; this area was characterized by few Purkinje neurons involving the molecular layer, whereas the granular layer was hypocellular and disorganized. The remainder of the cerebellar hemispheres was microscopically normal. Microscopic examination of the cerebral hemispheres, adjacent to the longitudinal fissure, revealed the absence of a corpus callosum, with small gyri that were more numerous than normal (polymicrogyria); the cerebral cortex was somewhat thinner in these areas. There were no gross or microscopic abnormalities of the spinal cord. From the Department of Veterinary Clinical Sciences (Wong, Winter, Sponseller, Schleining) and Veterinary Pathology (Haynes), College of Veterinary Medicine, Iowa State University,