Acute, Unilateral Transverse Sinus Occlusion During Craniectomy in Seven Dogs With Space-Occupying Intracranial Disease

Objective- The purpose of this study was to determine the effect of acute, unilateral transverse sinus occlusion on intracranial pressure (ICP) and postoperative mortality in dogs with structural intracranial disease.
Study Design- Affected dogs had a single transverse sinus occluded during craniectomy for intracranial mass biopsy or removal.
Animals- Seven dogs with space-occupying intracranial disease in the cerebellopontine angle area.
Methods- The ipsilateral transverse sinus was permanently occluded during the surgical approach to the intracranial lesion to increase surgical exposure by allowing a caudal lateral rostrotentorial craniectomy to be combined with a suboccipital craniectomy. In five dogs, intracranial pressure was monitored during surgery using a fiberoptic intracranial pressure monitoring device.
Results- Initial ICP varied among dogs, ranging from 7 to 21 mm Hg. Intracranial pressure, however, decreased in all dogs after craniectomy and durotomy ( P <.05). No increase in intracranial pressure occurred after transverse sinus occlusion ( P =.42). All dogs survived the surgical procedure.
Conclusions- Acute, unilateral transverse sinus occlusion during craniectomy in dogs with space-occupying intracranial lesions did not result in significant increases in ICP or intraoperative mortality.
Clinical Relevance- Acute, unilateral transverse sinus occlusion during craniectomy can be used to increased surgical exposure to the caudal fossa of the brain without increased risk of increasing ICP.     

The Effect of Acute, Unilateral Transverse Venous Sinus Occlusion on Intracranial Pressure in Normal Dogs

Lateral rostrotentorial and caudal suboccipital approaches to the brain were performed on six beagles. Intracranial pressure (ICP) was measured as the two craniectomies were connected by removing the bone of the nuchal crest and occluding the transverse venous sinus. Intracranial pressure remained constant after acute occlusion of the sinus with bone wax and there was no gross evidence of brain edema. All six dogs survived the surgery and five dogs survived for a minimum of 3 months. One dog died acutely during the postoperative period. The exact cause of the cerebellar hemorrhage and infarction found at necropsy in the latter dog was not evident. Anemia occurred in three of the six dogs as a result of intraoperative hemorrhage. All dogs surviving the perioperative period had mild, transient hypermetria and conscious proprioceptive deficits, but were neurologically normal 72 hours after surgery. Results of this study indicate that acute, unilateral transverse sinus occlusion is possible without an increase in ICP. The ability to do this allows access to the rostral aspect of the ipsilateral cerebellum and brain stem.     

Use of a titanium mesh for cranioplasty following radical rostrotentorial craniectomy to remove an ossifying fibroma in a dog

CASE DESCRIPTION: A 6-year-old Australian Terrier was evaluated for surgical removal of an ossifying fibroma of the left calvarium of 7 months' duration. CLINICAL FINDINGS: Computed tomography revealed invasion of the mass through the left parietal bone and extension into the epidural space of the brain. TREATMENT AND OUTCOME: A left rostrotentorial and frontal bone craniectomy was performed, and the mass was removed, along with a 1-cm margin of grossly normal bone. Cranioplasty was performed with a combination of porcine submucosa, titanium mesh, and screws. The dog recovered from surgery without complications and was discharged 3 days later. The dog was followed up for 24 months after surgery and has remained clinically normal. CLINICAL RELEVANCE: Findings suggested that rostrotentorial craniectomy is a viable option for removal of benign tumors affecting the parietal bones in dogs. Reconstruction of the resulting defect in the calvarium is possible with a combination of porcine submucosa and rigid titanium mesh.     

Intracranial abscess caused by Rhodococcus equi infection in a foal

CASE DESCRIPTION: A 4-month-old Missouri Fox Trotter colt was examined for a 5-week history of head tilt after treatment for suspected pulmonary Rhodococcus equi infection. CLINICAL FINDINGS: Computed tomography revealed osteolysis of the occipital, temporal, and caudal portion of the parietal bones of the left side of the cranium. A soft tissue mass compressing the occipital region of the cerebral cortex and cerebellum was associated with the osteolytic bone. TREATMENT AND OUTCOME: A rostrotentorial-suboccipital craniectomy approach was performed to remove fragmented occipital bone, debulk the intracranial mass, and obtain tissue samples for histologic examination and bacterial culture. All neurologic deficits improved substantially within 3 days after surgery. Bacterial culture of the resected soft tissue and bone fragments yielded R equi. CLINICAL RELEVANCE: Intracranial surgery in veterinary medicine has been limited to dogs and cats; however, in select cases, extrapolation of surgical techniques used in humans and small animals can assist with intracranial procedures in horses.     

Intraventricular tension pneumocephalus as a complication of transfrontal craniectomy: a case report

OBJECTIVE: To report the diagnosis and surgical treatment of a case of intraventricular tension pneumocephalus in a dog after a transfrontal craniectomy for removal of a falx cerebri meningioma. STUDY DESIGN: Case report. ANIMAL: A 12-year-old spayed English springer spaniel. RESULTS: Intraventricular air and a fistula between the craniectomy site and ventricular system were identified by magnetic resonance imaging. Prompt repair of the dural defect using prosthetic dura mater resulted in immediate regression of the neurological signs and cerebral spinal fluid rhinorrhea. Magnetic resonance imaging repeated 8 weeks after surgery showed complete resolution of pneumocephalus. CONCLUSIONS AND CLINICAL RELEVANCE: Tension pneumocephalus is an uncommon but life-threatening complication of craniectomy that requires urgent diagnosis and treatment.     

Surgical Treatment of a Canine Intranasal Meningoencephalocele

Objective— To report the clinical signs, diagnosis, and surgical treatment of an intranasal meningoencephalocele in a dog.
Study Design— Case report.
Animal— Female Border collie, 5 months old.
Methods— A right intranasal meningoencephalocele was identified by computed tomography and magnetic resonance imaging.
Results— The lesion was approached by a modified transfrontal craniotomy. Surgical closure of the defect at the level of the cribriform plate and removal of extruded brain tissue resulted in regression of lacrimation and coincided with absence of seizuring. Treatment with phenobarbital was gradually reduced and stopped at 7 months after surgery. At 28 months the dog remained free of seizures.
Conclusion— Meningoencephalocele, although rare, can cause seizures in dogs and can be treated surgically.
Clinical Relevance— A transfrontal craniotomy with excision of the meningoencephalocele and closure of the defect can be an effective treatment for an intranasal meningoencephalocele in dogs.     

Surgical approach for pinealectomy in the calf

Pinealectomy was performed on 7 calves, and a sham operation was performed on 3 calves. Two pinealectomized calves died immediately. The 5 remaining pinealectomized and 3 sham-operated control calves are presently involved in experimental studies. The surgical technique for exposure of the pineal gland was a rectangular (rostrotentorial) craniectomy between the median line and the horn bud. Removal of portions of the frontal and parietal bones, measuring 6 cm by 4 cm, provided adequate exposure. Positioning the head was important in order to gain the best access to the pineal gland. Water deprivation, hypertonic solution, elevation of the head, and hyperventilation prevented brain edema during the operation. The dura mater was sutured and glucocorticoids were administered to prevent postsurgical brain edema. Bone graft or plate was not placed over the craniectomy site. The soft tissue flap was repositioned over the dura mater and sutured in place--the periosteum and muscle comprising 1 layer and the skin a 2nd layer. Postsurgical complications were observed only in the 2 calves which died and were the result of hemorrhage and leukomalacia.     

ULTRASONOGRAPHIC ANATOMY OF THE TEMPOROMANDIBULAR JOINT IN HEALTHY PURE-BRED SPANISH HORSES

The objective was to describe the normal ultrasonographic appearance of the soft tissue and bony structures of the temporomandibular joint in Pure-Bred Spanish horses using frozen and plastinated sections performed as anatomical references. The temporomandibular joint of five healthy Pure-Bred Spanish horses and the head specimens from 12 Pure-Bred Spanish cadavers that were subjected to euthanasia for reasons other than temporomandibular joint problems were studied sonographically and anatomically. An 11 MHz linear-array transducer was used to obtain longitudinal ultrasonographic images of the temporomandibular joint from rostral, lateral, and caudal approaches. For anatomic study, a gross dissection was performed on six temporomandibular joints. The other six head specimens were first frozen at -30 degrees C for 48h and then, at -70 degrees C for a week. Three millimeter thick anatomic sections were collected in the same plane as the sonographic planes. These sections were plastinated, photographed, and compared with the corresponding ultrasonographic images. The articular surfaces, the articular cartilage, the disc, the intra-articular fat tissue, the joint capsule, and other structures were clearly visualized sonographically. Structures identified on the ultrasonographic images were in accordance with those identified on the corresponding anatomic sections. We confirmed the appearance of structures of the equine temporomandibular joint that have been described previously but we also identified the caudal fibrous expansion of the disc, the caudal compartment of the dorsal synovial pouch, and the lateral ligament. Our results define a reference that will aid in sonographic evaluation of the equine temporomandibular joint region.     

Clinical and MRI findings in three dogs with polycystic meningiomas

One spayed female Labrador retriever and two castrated male golden retrievers were evaluated for chronic (i.e., ranging from 3 wk to 24 wk) neurologic signs localizable to the prosencephalon. Signs included seizures, circling, and behavior changes. MRI demonstrated extra-axial, contrast-enhancing, multiloculated, fluid-filled, cyst-like lesions with a mass effect, causing compression and displacement of brain parenchyma. Differential diagnoses included cystic neoplasm, abscess or other infectious cyst (e.g., alveolar hydatid cyst), or fluid-filled anomaly (e.g., arachnoid cyst). The cyst-like lesions were attached to the rostral falx cerebri in all cases. In addition, case 2 had a second polycystic mass at the caudal diencephalon. Surgical biopsy (case 3 with a single, rostral tumor via transfrontal craniectomy) and postmortem histology (in cases 1 and 2) confirmed polycystic meningiomas. Tumor types were transitional (cases 1 and 3) and fibrous (case 2), with positive immunohistochemical staining for vimentin. Case 3 was also positive for E-cadherin, s100, and CD34. In all cases, staining was predominantly negative for glial fibrillary acid protein and pancytokeratins, supporting a diagnosis of meningioma. This report describes the first cases of polycystic meningiomas in dogs. Polycystic meningiomas are a rare, but important, addition to the differential diagnoses for intracranial cyst-like lesions, significantly affecting planning for surgical resection and other therapeutic interventions.     

Use of Computed Tomography in Standing Position to Identify Guidelines for Screw Insertion in the Distal Phalanx of Horses: An Ex Vivo Study

Objectives— To compare the precision of radiography and computed tomography (CT) preoperatively in the standing position for identification of guidelines for screw insertion in the distal phalanx, and to identify whether standing CT might improve operative time compared with preoperative radiographic planning.
Study Design— Experimental ex vivo study.
Animals— Cadaveric equine thoracic limb pairs (n=10).
Methods— Insertion of a 4.5 mm cortex screw in lag fashion into an intact distal phalanx was evaluated in 2 groups (n=10) of cadaveric equine thoracic limbs. In 1 group, the site, direction, and length of the implant were determined by radiography, and in the other group, by CT. Accuracy of screw placement was verified by specimen dissection. Outcomes were (1) absence of penetration of the articular surface, the solar surface, or the semilunar canal (2) appropriate length and direction of the screw. Surgical time was also measured.
Results— No screw penetrated the articular surface, the solar surface, or the semilunar canal in either group. CT was more accurate to identify guidelines for screw insertion (U=23.50, P =.049). With CT, surgical time (mean, 7.7 minutes) was significantly shorter (U=0.000, P =.000) than with radiography (mean, 12.7 minutes).
Conclusion— Standing CT can be used to accurately determine anatomic landmarks for screw insertion in lag fashion in sagittal fractures of the distal phalanx.
Clinical Relevance— This study has a clear clinical relevance for improved internal fixation of sagittal fractures of the distal phalanx.     

Successful surgical debridement of a cerebral Streptococcus equi equi abscess by parietal bone flap craniotomy in a 2-month-old Warmblood foal

Brain abscesses and intracranial masses have been regularly described in horses. Treatment often is difficult and unrewarding and mortality rate high. This case report describes the successful treatment of a cerebral abscess in a 2-month-old female Warmblood foal with severe neurological signs of acute onset. Computed tomography (CT) revealed a 3 × 4 × 4 cm cerebral mass in the left brain hemisphere with severe cerebral oedema. Craniotomy, using a parietal bone flap technique, allowed the abscess to be sampled, drained and lavaged. Immediately, post-surgery the foal showed significant clinical improvement. Sample culture confirmed Streptococcus equi equi infection. The foal was medically treated for 6 weeks, leading to complete clinical and radiographical recovery. Intracranial surgery in equine medicine is limited. Using a parietal bone flap instead of partial craniectomy to gain access to the cerebrum is a less invasive procedure leading to a better aesthetic result and should be considered for the treatment of cerebral masses in the horse.     

Surgical management of a canine intracranial abscess due to a bite wound

Objective – To describe the successful surgical management of a brain abscess in a dog secondary to bite wound. Case Summary – A 10‐year‐old neutered female Welsh Corgi/Chihuahua, weighing 5.3 kg, was presented for evaluation of seizures, ataxia, and falling to the left 8 days after a presumptive fight with another dog. On examination at presentation, the dog was alert, responsive, and ambulatory with tetra‐ataxia, falling to the left, left‐sided postural deficits, and absent left menace response. Within 24 hours, the dog progressed to nonambulatory tetraparesis with minimal motor, absent postural reactions of all limbs, left nasal hypalgesia, reduced gag reflex, and depressed mentation. Computed tomographic images of the brain were suggestive of a bite wound fracture of the right parietal bone with secondary meningoencephalitis, right parietal lobe abscessation, and white matter edema adjacent to the bone fracture. A modified right rostrotentorial craniectomy was performed, the abscess was identified, contents of the abscess were removed, and the surgical site was flushed extensively before closing. Corynebacterium spp. was cultured from within the abscess. Within hours of surgery, the dog was quiet but alert, responsive, and sitting up in her cage. In addition to surgical intervention, intensive care, broad‐spectrum IV antimicrobials, and supportive therapy led to significant neurologic improvement with only occasional seizures and mild postural reaction deficits of the left hindlimb remaining. New or Unique Information Provided – Abscess formation within the CNS is uncommon in dogs and cats and is associated with a high mortality rate. In veterinary medicine the management of brain abscesses is controversial with limited information available regarding treatment. This is the first case report that demonstrates surgical intervention in combination with antimicrobial therapy can be used successfully in the treatment of a canine brain abscess.     

Comparison of computer assisted surgery with conventional technique for treatment of abaxial distal phalanx fractures in horses: an in vitro study

Objective— To (1) evaluate and compare computer-assisted surgery (CAS) with conventional screw insertion (conventional osteosynthesis [COS]) for treatment of equine abaxial distal phalanx fractures; (2) compare planned screw position with actual postoperative position; and (3) determine preferred screw insertion direction.
Study design— Experimental study.
Sample population— Cadaveric equine limbs (n=32).
Methods— In 8 specimens each, a 4.5 mm cortex bone screw was inserted in lag fashion in dorsopalmar (plantar) direction using CAS or COS. In 2 other groups of 8, the screws were inserted in opposite direction. Precision of CAS was determined by comparison of planned and actual screw position. Preferred screw direction was also assessed for CAS and COS.
Results— In 4 of 6 direct comparisons, screw positioning was significantly better with CAS. Results of precision analysis for screw position were similar to studies published in human medicine. None of evaluated criteria identified a preferred direction for screw insertion.
Conclusion— For abaxial fractures of the distal phalanx, superior precision in screw position is achieved with CAS technique compared with COS technique.
Clinical Relevance— Abaxial fractures of the distal phalanx lend themselves to computer-assisted implantation of 1 screw in a dorsopalmar (plantar) direction. Because of the complex anatomic relationships, and our results, we discourage use of COS technique for repair of this fracture type.     

Incomplete Oblique Sagittal Fractures of the Dorsal Cortex of the Third Metacarpal Bone in Six Horses

Objective —To describe incomplete oblique sagittal dorsal cortical fractures of the equine third metacarpal bone, their surgical repair, and subsequent performance of the horses.
Study Design —Retrospective examination of medical records and racing performance.
Animal Population —Six Thoroughbred race horses, 2 to 4 years of age.
Methods —Radiographic confirmation of all fractures preceded general anesthesia and surgical correction. Three fractures were treated by intracortical compression using screws placed in lag fashion, and five fractures were treated by osteostixis. Race records were reviewed for each horse to determine performance after surgery.
Results —Fractures were best observed on palmarodorsal radiographic projections. Three horses treated by intracortical compression returned to racing, but fracture recurred in one horse and was treated by osteostixis. This horse and the other three horses treated by osteostixis raced after surgery.
Conclusions —Horses with incomplete oblique sagittal fractures of the dorsal cortex of the third metacarpal bone can race after surgical management of the fracture by screws placed in lag fashion or osteostixis. The authors' preferred surgical procedure for managing this fracture is osteostixis.
Clinical Relevance —Palmarodorsal radiographic projections of the third metacarpal bone are recommended in young Thoroughbred race horses suspected of having dorsal metacarpal stress fractures.     

MAGNETIC RESONANCE IMAGING AND CROSS SECTIONAL ANATOMY OF THE NORMAL EQUINE SINUSES AND NASAL PASSAGES

The purpose of this investigation was to define the magnetic resonance imaging anatomy of the rostral part of the equine head. 10 mm-thick, T1-weighted images of two isolated equine cadaver heads were obtained using a 1.5 Tesla magnet and a body coil. MR images were compared to corresponding frozen cross-sections of the cadaver head. Relevant anatomic structures were identified and labeled at each level. The resulting images provided excellent anatomic detail of the oral and nasal cavities, paranasal sinuses and associated structures. Annotated MR images from this study are intended as a reference for clinical MR imaging studies of the equine head.