Clinical and imaging findings in dogs with nerve root signature associated with cervical intervertebral disc herniation.

BACKGROUND: Intervertebral disc herniation (IVDH) is the most common spinal cord disease in dogs. Little information is available regarding the clinical presentation of nerve root signature (NRS) associated with cervical IVDH. HYPOTHESIS/OBJECTIVE: To detail the clinical and magnetic resonance imaging (MRI) findings in dogs with NRS associated with cervical IVDH. ANIMALS: Forty-seven client-owned dogs presenting with thoracic limb NRS and MRI confirmed IVDH. METHODS: Medical records from 2010 to 2020 were retrospectively reviewed for dogs that met inclusion criteria. Imaging studies were evaluated by 2 individuals to characterize location and severity of neural tissue compression. RESULTS: Chondrodystrophoid dogs comprised the majority of the study cohort, with dachshund the most common breed (n = 10). Three-quarters of dogs were ≥7 years of age. Interobserver agreement was moderate or good for all of the imaging variables evaluated. The C6-C7 intervertebral disc space was significantly overrepresented (P = .01), comprising 32% (15/47) of the affected discs. However, 42% (20/47) of cases involved C2-C3 though C4-C5 disc sites. Disc material was more frequently located laterally compared to medially within the vertebral canal (P = .0005), and to be associated with compression of the nerve root at the level of the intervertebral foramen (P = .012). CONCLUSION/CLINICAL IMPORTANCE: NRS is most commonly associated with lateralized or foraminal cervical disc herniations. It is most prevalent with C6-C7 intervertebral disc involvement, suggesting that there might be unique anatomic factors that contribute to development of NRS at this site, but can be a clinical manifestation of IVDH occurring anywhere along the cervical spine.

A lateral approach to the feline cerebellar fossa: case report and identification of an external landmark for the tentorium ossium.

OBJECTIVES: The aim of this study was to describe the use of an external landmark that defines the attachment of the tentorium ossium for planning a craniectomy to access the cerebellar fossa. The external landmark was defined by a line where the caudal aspect of the convexity of the cranium transitions to a flat surface in the caudal aspect of the temporal fossa. We also aimed to determine if this external landmark was present and readily visualized, and to establish its relationship to the nuchal crest using three-dimensional (3D) volume-rendered CT reconstructions created from cats with normal cranial morphology. METHODS: First, a case is presented for the description of an approach in a cat with a meningioma located dorsolateral to the cerebellum. Second, CT studies of five cats with normal cranial morphology were selected. Regions of interest (ROIs) were drawn at the attachment of the tentorium ossium to the cranium and nuchal crest. Three-dimensional reconstructions were developed with colored ROI overlays. The external landmark defined the tentorial attachment on all 3D reconstructions. Additionally, using the postoperative CT of the clinical case described herein, ROIs of the tentorial attachment and nuchal crest along with a third ROI, the craniectomy, were drawn and overlaid on the 3D reconstruction to illustrate the position of the craniectomy in relation to the tentorium ossium attachment and nuchal crest. RESULTS: The use of the external landmark provided for a craniectomy that enabled adequate visualization for excision of a meningioma. On all 3D reconstructions, the external landmark was present and readily visualized. CONCLUSIONS AND RELEVANCE: Between the attachment of the tentorium ossium and nuchal crest exists an area adequately sized for a craniectomy in cats. Clinicians can use an identifiable external landmark on the lateral aspect of the cranium to plan the rostral boundary for a craniectomy to access the cerebellar fossa in cats.

Differential effects on natural reward processing in rats after repeated heroin.

RATIONALE: Heroin users report reward deficits as well as reward enhancements (to drug stimuli). To better understand the causal relation between chronic heroin and alterations in natural reward processing, we used experimental techniques in animal models. METHODS: Separate groups of rats were trained in several food reward paradigms: conditioned place preference (CPP), food-reinforced lever pressing under a progressive ratio schedule of reinforcement, free feeding, and lever pressing with conditioned reinforcement. After training, the rats were subjected to 10 daily heroin (2 mg/kg) or saline vehicle injections and tested at 3, 15, and 30 days post-treatment. RESULTS: Repeated heroin treatment abolished the CPP and significantly reduced break points for food reward at 3, 15, and 30 days post-treatment. Repeated heroin did not affect free feeding. Finally, repeated heroin significantly enhanced responding for a food-based conditioned reinforcer. CONCLUSIONS: Repeated heroin decreases the attractiveness of food-associated cues and reduces motivation to work for natural reward. However, it appears to enhance natural conditioned reward processes that involve the acquisition of novel responding. Thus, repeated heroin appears to produce differential effects on natural reward processing depending on the nature of the reward-directed behavior.