NEUROMUSCULAR CASE OF THE MONTH - JULY 2006

Thoracic Limb Contractures, Regurgitation, and Urinary Incontinence in a 3 year old FS Boxer with Polymyositis
Contributed by Drs. Sophie Petersen, Maggie Knipe, Colette Williams,
and Monica Aleman
Veterinary Medical Teaching Hospital
University of California, Davis
Davis California


Clinical History

The dog first presented to the referring veterinarian in July 2005 for chronic regurgitation (since 4 months of age) and weight loss. It was managed for esophagitis with metaclopramide, sucralfate, and pepcid.  With frequent small feedings of canned food it regained some of the lost weight. The dog was then referred to the Internal Medicine Service at the Veterinary Medical Teaching Hospital (VMTH). The physical examination was unremarkable. CBC, thoracic radiographs, and urinalysis were all within normal limits. A chemistry panel showed  a mild elevation of ALT 154 (reference 19-67) and AST 152 (19-42). Creatine kinase (CK) was not performed on this visit. An esophagram showed accumulation of kibble within the caudal pharynx, delayed swallowing phase and poor primary esophageal motility. Esophageal endoscopy showed a nodular, irregular, mucosal surface with prominent vessels, while  the stomach appeared mildly edematous and friable with  pin  point ulcerations. Biopsies of the stomach showed inflammation with no evidence of etiology. The  acetylcholine receptor antibody titer was  negative. The dog was sent home on oral famotidine to help control esophagitis.

In January 2006 the dog was presented to the Orthopedic Service at the VMTH for a 2 months duration of progressive right thoracic limb lameness. The digits of the right thoracic limb were increasingly held  in a flexed position.  The left thoracic limb had been normal until  the past few days, but the owners were now starting to see a mild tendency for these digits  to flex as well. Physical examination showed mild temporal muscle atrophy, mild generalized right thoracic limb muscle atrophy, contracture of the right thoracic limb digits and carpus that could be manually extended, and pain associated with flexion and extension of the right shoulder. Radiographs of the right thoracic limb and spine were unremarkable and the dog was referred to the Neurology Service.

One week later the dog presented to the Neurology Service for further evaluation of right thoracic limb lameness (Fig. 1). By this time, the owners reported that the left thoracic limb was definitely affected. The dog was still regurgitating 1-2 times a day. The owners mentioned for the first time that the dog was urinary incontinent, which they managed with the dog wearing diapers around the house.  This was thought to have been a problem for as long as they owned the dog.

 

  Fig 1

Physical Examination

The Dog was bright, alert, responsive and well hydrated. T=101.5; P=140; R=panting, weight = 19.9 kg with  a body condition score of 4/9. The mucous membranes were pink and moist with a capillary refill time of <2s. Thoracic auscultation and abdominal palpation was unremarkable with no palpable lymphadenopathy.

Neurologic Examination

Mentation: Bright, alert, responsive and appropriate

Gait/posture: Ambulatory. The right thoracic limb was contracted distally making contact with the ground at the most doral tip of the nails/foot (Fig. 1). Marked  lameness was noted on the right thoracic limb.

Cranial nerves: Moderate atrophy was noted in the temporalis and masseter muscles bilaterally. Otherwise all cranial nerves were within normal limits.

Segmental reflexes: Biceps, triceps, and withdrawal reflexes were all present in the thoracic limbs; patellar, gastrocnemius reflexes, and withdrawal all  present in the pelvic limbs. Cutaneous trunci and perineal reflexes were intact.

Conscious proprioception: Could not be evaluated in the right thoracic limb but was present in the other three limbs.

Palpation: No apparent pain on palpation of the spine, manipulation of the neck or tail. Marked atrophy of the right thoracic limb (most notably triceps, but also antebrachial musculature), and mild atrophy of the same muscles in the left thoracic limb

Diagnostic Tests

CBC: Within normal limits

Chemistry panel: CK 1900 (reference 51-399), ALT 129 (reference 19-67),  AST 130 (reference 19-42)

Urinalysis (cystocentesis): SG 1.056; 5-10 wbc/hpf; many cocci

Thoracic radiographs: Unremarkable

Abdominal ultrasound: Thickened bladder wall, otherwise unremarkable

Urine Culture: Staphylococcus intermedius susceptible to all antibiotics tested

Electrodiagnostics

EMG showed increased spontaneous activity including positive sharp waves and fibrillation potentials in all muscles tested (right and left thoracic limb, right pelvic limb, trunk muscles, temporalis muscles), with the distal limb muscles more severely affected (Figs 2-4). Motor nerve conduction velocities were slightly below the reference range in the right pelvic and thoracic limbs.


Fig. 2 Left flexor carpii radialis.

 


Fig. 3 Right temporalis muscle.

Fig. 4 Right cranial tibial muscle .

 

Muscle Biopsies

Biopsies were collected from the left temporalis, triceps, and quadriceps muscles, and the right triceps muscle. The pattern of degeneration, regeneration, and mixed mononuclear cell infiltration was present within all four muscles with varying severity. Foci of mixed mononuclear cell infiltrates were present within the left quadriceps muscle (Fig. 5). Generalized atrophy, internal nuclei, and basophilic (likely regenerating)  fibers were present within the temporalis muscle (Fig. 6). Multifocal areas of endomysial fibrosis were also present (not shown). No organisms were identified.



Fig. 5 Left quadriceps muscle



Fig. 6 Left temporalis muscle

 

Diagnosis and Followup

Based on the pathological changes within the skeletal muscle biopsies and absence of detectable infectious agents, a diagnosis of immune-mediated  polymyositis was  made. The dog was started on prednisone at 2.5 mg/kg/day PO. The dog returned to  the VMTH for recheck examination in August 2006. At this time no lameness, regurgitation or urinary incontinence was found. On physical and neurological examination, there was no evident contracture in either limb. However, there was marked atrophy of the muscles of mastication and moderate atrophy of the right triceps muscle and distal musculature. At this time a gradual weaning off of prednisone was started. A telephone follow-up in September 2006 found that the dog was still doing very well, on anti-inflammatory doses of prednisone, and with no return of clinical signs.

 


Back to Top