MRI characteristics of fourth ventricle arachnoid diverticula in five dogs.

Intracranial arachnoid diverticula (cysts) are rare accumulations of cerebrospinal fluid (CSF) within the arachnoid membrane. The purpose of this retrospective study was to describe magnetic resonance imaging (MRI) characteristics of fourth ventricle arachnoid diverticula in a group of dogs. The hospital's medical records were searched for dogs with MRI studies of the brain and a diagnosis of fourth ventricle arachnoid diverticulum. Clinical characteristics were recorded from medical records and MRI studies were reinterpreted by a board-certified veterinary radiologist. Five pediatric dogs fulfilled inclusion criteria. Clinical signs included cervical hyperaesthesia, obtundation, tetraparesis, and/or central vestibular syndrome. In all five dogs, MRI findings were consistent with obstructive hydrocephalus, based on dilation of all ventricles and compression of the cerebellum and brainstem. All five dogs also had cervical syringohydromyelia, with T2-weighted hyperintensity of the gray matter of the cord adjacent to the syringohydromyelia. A signal void, interpreted as flow disturbance, was observed at the mesencephalic aqueduct in all dogs. Four dogs underwent surgical treatment with occipitalectomy and durotomy. A cystic lesion emerging from the fourth ventricle was detected in all four dogs during surgery and histopathology confirmed the diagnosis of arachnoid diverticula. Three dogs made excellent recovery but deteriorated shortly after surgery and were euthanized. Repeat MRI in two dogs revealed improved hydrocephalus but worsening of the syringohydromyelia. Findings from the current study supported theories that fourth ventricle arachnoid diverticula are secondary to partial obstruction of the central canal or lateral apertures and that arachnoid diverticula are developmental lesions in dogs.

Ethanol poisoning as a differential diagnosis in a hunter's dog with tetraplegia.

A 4.5-month-old German pointer was presented with tetraplegia. Based on the physical examination, a tentative diagnosis of idiopathic polyneuropathy or synaptic disorder was made. Later that day additional information from the owner revealed that the dog might have ingested sloe berries that had been used to make sloe gin. Ethanol poisoning was added to the differential diagnosis. The dog's locomotion recovered in the course of 24 hours. Faecal analysis revealed that the animal had ingested at least 127 gin-saturated sloe berries and it was estimated that the blood ethanol concentration would have been at least 0.75 per thousand. The aetiology, diagnosis, and treatment of ethanol poisoning in dogs is reviewed.

Cervical myelopathy due to complex Atlanto-axial malformation including partial atlantal dorsal arch aplasia in a domestic rabbit.

A 1-year-old dwarf rabbit was presented with sub-acute progressive tetraparesis. Radiography, CT and MRI revealed compressive cervical myelopathy secondary to a complex atlanto-axial malformation including partial aplasia of the atlantal dorsal arch, dens malformation, malarticulation and lateral atlanto-occipital displacement. Owners decided against surgical treatment and elected conservative treatment including analgesia with non-steroidal anti-inflammatory drugs, cage rest and physiotherapy. Within 2 months clinical signs deteriorated and the owner elected euthanasia. Subsequent necropsy confirmed imaging findings. Similar cases described in humans and dogs suggest that partial aplasia of the dorsal arch of the atlas might often be an asymptomatic radiologic finding in these species. In contrast, this first description of a similarly affected rabbit demonstrates that complex atlanto-axial malformations can cause severe clinical signs.

Diagnosis and treatment of a chronic atlanto-occipital subluxation in a dog.

A 6-year-old Labrador retriever-cross was evaluated for an abnormal gait and head carriage 6 weeks after suffering trauma. The dog was presented with an ambulatory tetraparesis and was reluctant to move his head. Myelography and computed tomography demonstrated a subluxation of the atlanto-occipital joint with compression of the spinomedullary junction and the brain stem by the occipital bone. Removal of the compressive part of the occipital bone resulted in improvement of the clinical signs within 6 weeks, and resolution of clinical signs occurred 8 months after surgery.

Compressive myelopathy due to intervertebral disk extrusion in a llama (Lama glama).

A 12-year-old intact female llama was euthanized following acute onset of spastic tetraparesis and recumbency with inability to rise. Postmortem examination revealed caudal cervical spinal cord compression due to a mass within the ventral spinal canal arising from the C6-C7 intervertebral disk space and attached to an irregularly thickened annulus fibrosis. On histopathologic examination, the mass was composed of amorphous acellular basophilic to amphophilic material admixed with irregularly arranged collagen bundles. The amorphous material was metachromatic and contained multiple small foci of markedly vacuolated round cells, characteristic of origin from the nucleus pulposus. Severe necrosis of all white matter tracts with astrocytic reaction was present in the overlying spinal cord segment. Ascending and descending Wallerian degeneration and dissecting interstitial astrogliosis were present within white matter tracts above and below the lesion, respectively. The diagnosis was compressive myelopathy due to chronic extrusion of the nucleus pulposus of the C6-C7 intervertebral disk. To the authors' knowledge, this is the first report of intervertebral disk disease in a camelid.

Fibrocartilaginous embolism in a chondrodystrophoid breed dog.

An 8-year-old intact male Shih Tzu dog was admitted with acute-onset tetraplegia. Magnetic resonance imaging showed an abnormality of the cervical intramedullary spinal cord. Histopathological examination of a spinal biopsy confirmed the presence of intravascular cartilaginous emboli. This is the first report of an antemortem diagnosis of fibrocartilaginous embolism in a chondrodystrophoid breed dog.

Discal cysts of the cervical spine in two dogs.

Discal cysts, which lie directly over intervertebral discs, are rare. Two old dogs with tetraparesis were referred to our facility. In both animals, magnetic resonance imaging revealed intraspinal extradural cystic mass lesions that were dorsal to degenerative intervertebral discs at the C3-C4 level. These lesions had low signal intensity on T1-weighted images, and high signal intensity on T2-weighted images. A ventral slot approach was used to perform surgical decompression, after which the symptoms improved remarkably. Discal cysts should be included in the differential diagnosis of dogs with cervical pain and tetraparesis. One effective treatment for discal cysts is surgical intervention.

Hydrated nucleus pulposus herniation in seven dogs.

The clinical signs, magnetic resonance imaging (MRI) findings, treatment and follow-up in seven dogs with hydrated nucleus pulposus extrusion (HNPE) are reported. All dogs had tetraparesis or tetraplegia. T2-weighted MRI revealed extradural hyperintense homogeneous material compressing the cervical spinal cord. After conservative treatment (five dogs) or surgical decompression (two dogs), all dogs returned to ambulatory function within 1 month. Follow-up MRI in conservatively treated dogs revealed complete disappearance of the extruded material. Histopathological examination of surgical specimens confirmed that the retrieved material was extruded nucleus pulposus with evidence of early degeneration.

Spinal cord injury secondary to electrocution in a dog.

A 13-year-old, female spayed, crossbreed dog of 32 kg was presented for evaluation of peracute onset of non-ambulatory tetraparesis after chewing an electrical wire. Neurological examination was consistent with a C1-C5 myelopathy. Magnetic resonance imaging revealed a focal intramedullary lesion over the C2-C3 vertebral bodies, which was confirmed to be an acute focal necrotising poliomyelopathy with subarachnoid and subdural haemorrhages on postmortem examination. This report describes the clinical, imaging and histopathological findings of this unusual type of spinal cord injury, and the effects of electrocution in the central nervous system of dogs.

A comparison of equid herpesvirus-1 (EHV-1) vascular lesions in the early versus late pregnant equine uterus.

Four Welsh Mountain pony mares at 3 months of gestation and one mare at 5 months were inoculated intranasally with equid herpesvirus-1 (EHV-1: Ab4 isolate) at doses of 10(5) to 10(6.6) TCID50. All five mares became infected, but no cases of paresis or abortion occurred. On days 8, 9, 11, 12 (3-month-pregnant mares) and 13 (5-month-pregnant mare) after infection, a detailed examination of the pregnant uterus was made. Small numbers of vascular lesions with EHV-1 antigen expression in endothelial cells were present in the uteri of the early gestational mares; thrombi were rare and foci of thromboischaemic damage were not seen. Six pony mares previously inoculated with EHV-1 Ab4 at 9 months of gestation had a significantly greater degree of vascular abnormality than that found in the four mares infected at 3 months of gestation, but the degree of EHV-1 antigen expression and thrombosis in the uterus was similar to that found in the single mare infected when 5 months pregnant.

Clinical and neuropathological features of West Nile virus equine encephalomyelitis in Italy.

West Nile (WN) virus infection is a mosquito-borne flavivirosis endemic in Africa and Asia. Clinical disease is usually rare and mild and only in a few cases the infection causes encephalomyelitis in horses, fever and meningoencephalitis in man. We report here the clinical and pathological findings in an epidemic of the disease involving 14 horses from Tuscany, Italy. All cases were observed from August to October 1998. Affected horses showed ataxia, weakness paresis of the hindlimbs and, in 6 cases, there was paraparesis progressing to tetraplegia and recumbency within 2 to 9 days. Eight animals recovered without any important consequences. Serological investigations revealed positivity to WN virus in all the 14 horses and the agent was isolated from the cerebellum and spinal cord of an affected horse. Postmortem examination was carried out on 6 horses. The neuropathological pattern was that of a mild to moderate, nonsuppurative polioencephalomyelitis with constant involvement of the ventral horns of the thoracic and lumbar spinal cord, where focal gliosis and haemorrhage were also apparent in some cases. Differential diagnoses with other equine viral encephalomyelitides are discussed. Climatological and environmental characteristics of the geographic area in which the outbreaks occurred suggest the existence of suitable conditions for the development of the disease. This is the first report of WN virus equine encephalomyelitis in Italy.

Idiopathic polyneuropathy in Alaskan malamutes.

Clinical and morphologic features of a progressive polyneuropathy in young mature Alaskan Malamutes are described. Clinical signs included progressive paraparesis, synchronous pelvic limb gait, exercise intolerance, hyperesthesia, hyporeflexia, muscle atrophy, and tetraplegia. Electromyographic testing revealed diffuse fibrillation potentials and positive sharp waves in limb muscles, especially in muscles below the elbow and stifle. Pathologic findings in skeletal muscles and peripheral nerves included neurogenic muscle atrophy, focal or diffuse loss of myelinated nerve fibers, myelinoaxonal necrosis, and variable demyelination or remyelination. Ultrastructural changes included axonal degeneration, presence of numerous Büngner bands, and denervated Schwann cell subunits. The nature and distribution of abnormal electrophysiologic and pathologic findings were suggestive of a distal sensorimotor polyneuropathy, which we have termed idiopathic polyneuropathy of Alaskan Malamutes to distinguish this condition from hereditary polyneuropathy of Norwegian Alaskan Malamutes, last described in 1982.

Acute idiopathic polyneuropathy in the dog.

From among a large group of dogs with acute tetraparesis, we identified 10 dogs with a distinct peripheral nerve disorder. Prior to the onset of signs, all of the dogs had been healthy, and none was known to have been exposed to a neurotoxin or raccoon bite. Weakness, with hypoactive or absent segmental reflexes, became progressively worse for 1 to 21 days. Results of electromyography and nerve conduction studies invariably were compatible with a diagnosis of polyneuropathy that predominantly affected proximal nerve segments. Appearance of nerve biopsy specimens and the short time course for functional recovery suggested a demyelinative component to the disorder. The extent of recovery was variable but often rapid and complete in dogs that did not succumb to complications in the early period. Corticosteroid therapy did not demonstrably influence the outcome. This acute idiopathic polyneuropathy in the dog shares many clinical and pathologic features with idiopathic polyradiculoneuritis (Coonhound paralysis).

Depressed thyroid function in two tetraplegic dogs.

Rapidly progressing tetraplegia developed in two 6-year-old dogs, both of which had eaten decayed meat sometime during the 24 hours prior to the onset of paralysis. Both dogs were found to have depressed thyroid function, as indicated by extremely low triiodothyronine (T3) and thyroxine (T4) values. Electromyographic studies revealed some abnormal insertional activity but no abnormal potentials when the fore- and hindlimb muscles were at total rest. Nerve conduction velocity was slightly depressed in 1 of the dogs and severely depressed in the other. Recovery was complete in less than 3 weeks in 1 dog, but the other dog was not completely recovered when placed under the owner's care 2 1/2 months after admission.

Observation of a secondary compressive lesion after treatment of caudal cervical spondylomyelopathy in a dog.

In a 7-year-old Doberman Pinscher with an atactic gait, neurologic examination revealed tetraparesis, conscious proprioceptive deficits, and rigid ventral flexion of the neck. Radiography and myelography revealed a ventral, extradural, dynamic compressive lesion between C6 and C7. Distraction decompression was performed, using cancellous bone screws and methylmethacrylate. After initial improvement, clinical signs recurred 2 weeks after surgery and progressed until the dog was euthanatized 6 weeks after surgery. Postmortem myelography revealed an extradural compressive lesion adjacent to the implant, between C5 and C6. Secondary compressive lesions induced by surgical or biomechanical alterations of the cervical portion of the spine may be complications of treatment of caudal cervical spondylomyelopathy.

Tetraparesis following cervical disk fenestration in two dogs.

Two dogs were nonambulatory and tetraparetic following cervical disk fenestration used as the treatment for cervical disk disease. Severe pain and cervical muscle fasiculation also were evident. The site of disk extrusion was localized radiographically, and cervical ventral decompression was used to remove the disk material. Recovery in both cases was complete.

Cervical fibrotic stenosis in a young Rottweiler.

An 18-month-old neutered male Rottweiler was examined because of slowly progressive spastic tetraparesis and ataxia. Signalment and clinical signs were suggestive of 2 neuronal degenerative diseases presumed to be inherited in young Rottweilers: leukoencephalomyelopathy and neuroaxonal dystrophy. Myelography revealed an extradural compression at the articulation of the second and third cervical vertebrae. At surgery, focal hypertrophy of the yellow ligament was observed to compress the spinal cord ventrally at that site.

Parasitic laryngeal papillomatosis in a horse.

Papillomatous lesions intruding into the laryngeal airway were identified in an imported polo pony during a routine neurological examination for partial quadriplegia. Histological examination established a diagnosis of laryngeal besnoitiosis but it is unlikely that the laryngeal parasitism was associated with the cerebellar neuropathy which was also present.

Progressive tetraparesis and laryngeal paralysis in a young rottweiler with neuronal vacuolation and axonal degeneration: an Australian case.

A 5-month-old female Rottweiler dog was diagnosed to have a neurodegenerative disease that has been recently reported in Rottweilers from North America and Europe. The dog was presented with progressive signs of ataxia, tetraparesis and inspiratory stridor. The clinical investigation included analysis of CSF, radiography, myelography and electrophysiological testing. No evidence of vertebral malformation or inflammatory CNS disease was identified. Bilateral laryngeal paralysis was identified in the lightly anaesthetised dog. Electromyography showed abnormal spontaneous activity from the intrinsic musculature of the larynx. At necropsy there were no gross abnormalities of the nervous system but there was atrophy of the dorsal cricoarytenoid muscles of the larynx. There were widespread histological abnormalities throughout the nervous system including neuronal vacuolation, spongiform changes in the neuropil and axonal degeneration which was most prominent in the spinal cord. These clinical and pathological findings are consistent with the diagnosis of a new neurodegenerative disease reported from North America and Europe. This diagnosis is of particular significance in Australia where transmissible spongiform encephalopathies have not been identified.

Acute onset quadriparesis as a sequela to an oropharyngeal stick injury.

A three-year-old male neutered crossbred dog was referred for investigation of acute onset quadriparesis, which had occurred following an oropharyngeal stick injury. Myelography revealed a right-sided extradural lesion overlying the C5/6 intervertebral disc space. A dorsolateral hemilaminectomy was performed at this site and two fragments of wood were removed from the vertebral canal adjacent to the spinal cord. The dog was ambulatory with right-sided forelimb monoparesis within a week of surgery and improved further following discharge. Three months following surgery, the dog was exercising freely with only mild right forelimb lameness.