Degeneration of autonomic nervous system in feline dysautonomia case

Transcription

1 Vet Times The website for the veterinary profession Degeneration of autonomic nervous system in feline dysautonomia case Author : VICKI BROWN Categories : Vets Date : March 10, 2008 VICKI BROWN discusses the case study of a British blue cross cat presenting with depression and anorexia A FIVE-year-old male neutered British blue cross cat arrived having become progressively depressed and anorexic over the past three days. It had regurgitated twice that morning and had appeared to be straining to pass faeces indoors, which was most out of character as the cat usually defecated outdoors. For the past 24 hours the third eyelids had become prominent, especially in the left eye. Clinical examination - Temperature: 38.1 C. - Pulse: 120 per minute. - Respiration: 36 per minute. The cat was moderately dehydrated and the nose was slightly dry. In addition to the third eyelids protruding, the pupils were also dilated and had no pupillary light reflex. Menace and palpebral reflexes were intact, ophthalmic examination revealed no abnormalities and vision was deemed normal. The conjunctiva were mildly hyperaemic. 1 / 10

2 Other mucous membranes were a normal colour, and CRT was two seconds. A Schirmer tear test (STT) revealed reduced tear production in both eyes: the left eye had a flow of 7mm per minute and the right was 10mm per minute. Peripheral lymph nodes were normal and auscultation of the heart and lungs revealed no abnormalities. Palpation of the abdomen revealed constipation. Proprioceptive responses appeared to be normal, although it was thought that anal tone was reduced. Problem list and differential diagnosis Regurgitation - Megaoesophagus: idiopathic, myasthenia gravis, polyneuropathy (such as FD), systemic lupus erythematosus or toxicosis. - Motility disorder. - Foreign body. - Stricture: intraluminal lesion and extraluminal compression. - Oesophagitis. - Hiatal disorder. - Oesophageal neoplasia. - Oesophageal diverticulum. Constipation and faecal tenesmus - Dietary: foreign material in faeces. - Obstruction: extraluminal - perirectal/perianal tumour, perineal hernia and pelvic fracture; intraluminal - neoplasia, granuloma, diverticulum/prolapse and foreign body. - Neuromuscular: lumbosacral cord disease, bilateral pelvic nerve injury, dysautonomia, CNS disease (lead), idiopathic megacolon and cauda equina syndrome. - Dehydration. - Metabolic disorders: hypokalaemia, hypercalcaemia, hyperparathyroidism and phaechromocytoma. 2 / 10

3 - Painful defection: anal sac abscess, perianal fistula, anorectal stricture/tumour, proctitis, spinal injury and pelvic injury. Keratoconjunctivitis sicca, mydriasis and protruding third eyelids - Dysautonomia. - Toxoplasmosis. - Hypocalcaemia. - Retrobulbar lesion/tumour. - Glaucoma. - Toxicosis. - Tetanus. Anorexia - Dietary/oral disorder - not applicable. - Systemic disease causing inappetence. Depression - GI tract disease as primary cause - for example, leading to systemic infection. - Systemic disease with secondary GI disease - for example, dysautonomia. Investigation Initially, blood haematology and biochemistry were performed ( Table 1 ). This revealed haemoconcentration and hyperproteinaemia, which reflected the patient s dehydration. FeLV and FIV tests were negative and a blood smear was unremarkable. After 24 hours of intravenous fluids, the cat was hydrated and brighter and had passed faeces. A test meal was fed to the cat but was regurgitated within five minutes of consumption. The cat was then anaesthetised with propofol and maintained with isoflurane carried in oxygen. A stomach tube administered 10ml of barium paste, and a lateral thoracic radiograph was taken. This 3 / 10

4 revealed oesophageal dilation and no sign of aspiration pneumonia. As cost was of concern to the owner, no further radiographs were taken. The ocular response to 0.1 per cent pilocarpine and the third eyelid response to 1: 10,000 epinephrine was assessed - comparing the results with a control cat ( Table 2 ). These revealed denervation hypersensitivity. Following these investigations, feline dysautonomia was sus pected and so a clinical scoring system was drawn up. Following this, the patient scored 11. Diagnosis: feline dysautonomia. Prognosis: guarded. Treatment The patient was given intravenous Hartmann s solution (Aquapharm number 11, Animalcare) at a rate of 10ml/kg/hour for two hours. The drip rate was then slowed to 4ml/kg/hour. Hypromellose 0.3 per cent (non-proprietary) eye drops were given every two hours. Pilocarpine one per cent (nonproprietary) eye drops were given every eight hours to aid oronasal and lacrimal secretion. A dose of 3mg metoclopramide hydrochloride (Emequell, Pfizer) was given by intravenous infusion to improve gastric emptying. A liquid paraffin enema was administered. Food and water were withheld. After 24 hours the cat had defecated successfully. Intravenous fluids were ceased and the patient was started on cisapride tablets (Prepulsid, Janssen-Cilag) at a dose rate of 5mg BID (100?g/ kg). A test meal was regurgitated. A naso-oesophageal tube was placed to prevent aspiration of oesophageal contents. Follow-up Regular small meals per os were offered from a raised platform from the third day of treatment. Regurgitation was significantly reduced with the aid of cisapride, although not entirely eliminated. The cat was discharged on cisapride, pilocarpine and hypromellose (as above). Two weeks later the cat was doing well and gaining weight. Constipation was present intermittently and the owner was provided with white soft paraffin 475mg/g (Katalax, C-Vet VP) to administer as necessary (half to one inch of paste one to two times daily). Six weeks later the cat re-presented in a very depressed state, with severe dyspnoea and crusting around the nose. The owner had not re-ordered cisapride when the supply had finished and the cat was regurgitating after every meal. For the past two days it had been anorexic, and was severely dehydrated on presentation. 4 / 10

5 Constipation was marked, the coat was very poor, and the eyes were crusted. Auscultation of the lungs revealed consolidation of the ventral lobes and aspiration pneumonia was strongly suspected. Although emergency treatment was offered, the owner declined and the cat was euthanised. Permission for postmortem examination was refused. Discussion Feline dysautonomia is a disease of domestic cats characterised by extensive degeneration of the autonomic nervous system (Cave, 2003). Within a few days, clinical signs develop, characterised by regurgitation, constipation, dilated pupils (which are unresponsive to light) prolapsed third eyelids and reduced tear secretion (Sharp et al, 1984). Feline dysautonomia was first reported in 1982 in the UK but has now also been seen sporadically in the US, other European countries, New Zealand and the United Arab Emirates (Sharp et al, 1984). Feline dysautonomia appears to be one of a group of primary dysautonomias affecting dogs, hares, rabbits and horses. These diseases have very similar pathophysiology. To date, the causes of this group of diseases remains unknown (Cave, 2003). Although differential diagnoses are few in cats with multiple cardinal clinical signs, definitive diagnosis requires histopathological examination of autonomic ganglia at postmortem. It is not known how sensitive and specific the clinical scoring system for antemortem diagnosis is ( Table 3 ). Ideally, thoracic radiology should be performed with the cat conscious as sedation and anaesthesia can cause megaoesophagus. However, adequate restraint of the patient in the conscious state was not possible in this case. As the aetiology of feline dysautonomia is unknown, treatment is symptomatic. Pilocarpine is an autonomic stimulant; potential side effects (abdominal cramps and muscle fasciculations) were not seen in this case. Metoclopramide improves gastric emptying in feline dysautonomia (Sharp and Gookin, 1995). In a study by Cave et al (2003), no improvement in oesophageal motility was detected by fluoroscopy in cats treated with cisapride (1mg/kg every eight hours per os) but increased rates of regurgitation were noted when it was withdrawn seven days during chronic management. Original reports described survival in less than 30 per cent of cases (Sharp et al, 1984). However, more recent studies show that in less severely affected cats survival rates are higher (Blaxter and Gruffydd-Jones, 1987). Heart rate measurement may be a prognositic indicator; heart rates in surviving cats were higher (Cave et al, 2003). In this case the heart rate was at the low end of the reference range. References 5 / 10

6 Blaxter A and Gruffydd-Jones, T (1987). Feline dysautonomia, In Practice 9: Cave T A, Knottenbelt C et al (2003). An outbreak of feline dysautonomia (Key-Gaskell syndrome) in a closed colony of pet cats, The Veterinary Record 153: (13) Sharp N J H, Nash, A S et al (1984). Feline dysautonomia (the Key-Gaskell syndrome): a clinical and pathological study of 40 cases, Journal of Small Animal Practice 25: Sharp N J H, and Gookin j l (1995). Visceral and bladder dysfunction and dysautonomia. In Wheeler S J (ed), Manual of Small Animal Neurology (2nd edn), BSAVA publications, London: / 10

7 A healthy well fed British blue cat. Clinical signs of feline dysautonomia are regurgitation, constipation, dilated pupils, prolapsed third eyelids and reduced tear secretion. 7 / 10

8 TABLE 1. Blood haematology and biochemistry 8 / 10

9 TABLE 2. Ocular pharmacological tests (after Cave, 2003) 9 / 10

10 Powered by TCPDF ( TABLE 3. Clinical scoring system for feline dysautonomia (ater Sharp and Gookin, 1995) 10 / 10