Results of cerebrospinal fluid analysis, neurologic examination findings, and age at the onset of seizures as predictors for results of magnetic resonance imaging of the brain in dogs examined because of seizures: 115 cases (1992-2000)

OBJECTIVE: To determine whether neurologic examination findings, results of CSF analysis, or age at the onset of seizures could be used to predict whether results of magnetic resonance imaging (MRI) would be normal or abnormal in dogs with seizures. DESIGN: Retrospective study. ANIMALS: 115 dogs. PROCEDURE: Information on results of neurologic examination, results of CSF analysis, age at the onset of seizures, and results of MRI was obtained from the medical records. RESULTS: Results of MRI were abnormal in 61 dogs and normal in 54. Sensitivity and specificity of neurologic examination alone were 77 (47/61) and 91% (49/54), respectively. Sensitivity and specificity of CSF analysis alone were 79 (48/61) and 69% (37/54), respectively. Results of MRI were abnormal for 12 of 28 (43%) dogs with abnormal CSF analysis results and normal neurologic examination results but for only 2 of 35 (6%) dogs with normal CSF analysis and normal neurologic examination results. Similarly, results of MRI were abnormal for 36 of 37 (97%) dogs with abnormal CSF analysis and abnormal neurologic examination results but for only 11 of 15 (73%) dogs with normal CSF analysis results and abnormal neurologic examination results. Age at the onset of seizures (< 6 vs > or = 6 years old) was not significantly associated with results of MRI. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that neurologic examination findings and results of CSF analysis are useful in predicting whether results of MRI will be abnormal in dogs examined because of seizures, but age at the onset of seizures is not.     

Management of hypertension controls postoperative neurologic disorders after renal transplantation in cats

OBJECTIVES: To determine the prevalence and describe the management of hypertension and central nervous system (CNS) complications after renal transplantation in cats. We also compared the prevalence of CNS complications between cats monitored and treated for postoperative hypertension and a previously described, historical control group of cats not monitored or treated for postoperative hypertension. STUDY DESIGN: Retrospective clinical study. ANIMALS OR SAMPLE POPULATION: A total of 34 client-owned cats that received renal allografts for the treatment of end-stage renal failure. METHODS: Medical records were reviewed. Data obtained included preoperative and postoperative systolic blood pressures, antihypertensive therapy, response to treatment, neurologic signs, and clinical outcome. The results were compared with a historical control group of feline renal allograft recipients that were neither monitored nor treated for postoperative hypertension. RESULTS: Severe postoperative hypertension occurred in 21 of 34 of cats. Hypertension was treated in all 21 cats with subcutaneously administered hydralazine which reduced systolic blood pressure to less than 170 mm Hg in 15 minutes in 20 of 21 cats; hydralazine produced hypotension in one cat and failed to control hypertension in 1 cat. After transplantation, seizures were observed in one cat and other neurologic complications (stupor, ataxia, and central blindness) were observed in three cats. The prevalence of seizures and neurologic complication-related deaths after transplantation was significantly reduced with treatment of postoperative hypertension. CONCLUSIONS AND CLINICAL RELEVANCE: Hypertension is a major contributing factor to postoperative seizure activity after renal transplantation in cats; treatment of hypertension reduces the frequency of neurologic complications.     

Polioencephalomyelitis in cats.

Six cats with chronic progressive neurologic signs of ataxia, paresis, tremors, pupillary abnormalities and seizures had polioencephalomyelitis of probable viral origin. Lesions were most severe in the spinal cord. The uniformity in distribution and nature of the lesions in all six cats strongly suggested a common cause. The condition was compared with other viral infections of known and unknown cause.     

Clinical signs, underlying cause, and outcome in cats with seizures: 17 cases (1997-2002)

OBJECTIVE: To determine clinical signs, results of diagnostic testing, underlying cause, and outcome in cats with seizures. DESIGN: Retrospective study. ANIMALS: 17 cats with seizures. PROCEDURE: Only those cats in which an underlying metabolic abnormality causing the seizures had been identified, diagnostic imaging of the brain and CSF analysis had been done, or a necropsy had been performed were included. Seizures were classified as being a result of metabolic disease, symptomatic epilepsy (ie, epilepsy resulting from a structural lesion of the brain), or probably symptomatic epilepsy (ie, epilepsy without any extracranial or identifiable intracranial disease that is not suspected to be genetic in origin). RESULTS: 3 cats had seizures associated with an underlying metabolic disease (hepatic encephalopathy), 7 had symptomatic epilepsy (3 with neoplasia and 4 with meningoencephalitis), and 7 had probably symptomatic epilepsy. Six of the 7 cats with symptomatic epilepsy died or were euthanatized within 3 months after the diagnosis was made, whereas 6 of the 7 cats with probably symptomatic epilepsy survived for at least 12 months after the diagnosis was made. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that cats with probably symptomatic epilepsy may have a good long-term prognosis.     

Use of anti-coronavirus antibody testing of cerebrospinal fluid for diagnosis of feline infectious peritonitis involving the central nervous system in cats

OBJECTIVE: To assess the use of measuring anti-coronavirus IgG in CSF for the diagnosis of feline infectious peritonitis (FIP) involving the CNS in cats. DESIGN: Prospective study. SAMPLE POPULATION: CSF and serum samples from 67 cats. PROCEDURES: CSF and serum samples were allocated into 4 groups: cats with FIP involving the CNS (n = 10), cats with FIP not involving the CNS (13), cats with CNS disorders caused by diseases other than FIP (29), and cats with diseases other than FIP and not involving the CNS (15). Cerebrospinal fluid was evaluated for concentrations of erythrocytes, leukocytes, and total protein. Anti-coronavirus IgG was measured in CSF and serum by indirect immunofluorescence assay. RESULTS: CSF IgG (range of titers, 1:32 to 1:4,096) was detected in 12 cats, including 6 cats with neurologic manifestation of FIP, 4 cats with FIP not involving the CNS, and 2 cats with brain tumors. Cerebrospinal fluid IgG was detected only in cats with correspondingly high serum IgG titers (range, 1:4,096 to 1:16,384) and was positively correlated with serum IgG titers (r = 0.652; P < 0.01), but not with any other CSF parameter. Blood contamination of CSF resulted in < or = 333 erythrocytes/microL in cats with CSF IgG. CONCLUSIONS AND CLINICAL RELEVANCE: The correlation between serum and CSF IgG and the fact that CSF IgG was detected only in strongly seropositive cats suggested that CSF anti-coronavirus IgG was derived from blood. Measurement of anti-coronavirus IgG in CSF was of equivocal clinical use.     

Reference intervals for feline cerebrospinal fluid: cell counts and cytologic features

Reference intervals for feline CSF cell counts and cytologic variables were determined. Values were derived from 58 adult cats that had normal neurologic examination findings and did not have histologic lesions of the CNS. Effect of age or gender was not apparent for any CSF variable, and no CSF variable was significantly correlated with its corresponding blood value. Total WBC count and neutrophil and eosinophil percentages were positively correlated with the CSF RBC count. Thus, proposed reference intervals for feline CSF were derived from 33 cats with CSF RBC count of less than 31 cells/ul. Data for CSF samples with range between 31 and 1,700 RBC/microliters were also determined. Erythrocyte count was not significantly different in CSF collected, using 20- or 22-gauge spinal needles.     

Outcomes of pituitary tumor irradiation in cats

BACKGROUND: Information on tumor control and normal tissue effects of radiotherapy to treat pituitary tumors in cats is limited. HYPOTHESIS: Radiation therapy is effective in controlling the clinical signs associated with pituitary tumors in cats, with a low incidence of adverse effects. ANIMALS: Eight cats were irradiated at Colorado State University between 1991 and 2002 for spontaneous pituitary tumors. METHODS: A retrospective review of records was made to assess tumor control and incidence of radiation-induced adverse effects. RESULTS: Pituitary carcinoma was diagnosed in 2 cats and pituitary adenoma in 6 cats. Total radiation dosage ranged from 4,500 to 5,400 cGy administered Monday through Friday in 270 or 300 cGy fractions. Acute effects were limited to epilation and mild otitis externa. Focal brain necrosis adjacent to regrowth of a pituitary carcinoma and a second tumor in the radiation field were reported as possible late effects. Median survival, regardless of cause of death of the 8 cats, was 17.4 months (range, 8.4 to 63.1 months). Median survival could not be determined if cats were censored for non-tumor-related causes of death. Six cats were alive at 1 year, and 3 cats were alive at 2 years after treatment. Tumor recurrence was seen in 1 cat with a pituitary carcinoma. Neurologic signs improved within 2 months in all 5 cats that presented with abnormal neurologic signs. Clinical signs caused by a concurrent endocrine disorder began to improve within 1-5 months in the 7 cats with hyperadrenocorticism or acromegaly. CONCLUSIONS AND CLINICAL RELEVANCE: Radiation therapy is an effective primary treatment modality for cats presenting with neurologic signs associated with a pituitary mass and can improve clinical signs associated with concurrent hyperadrenocorticism or acromegaly in cats with no neurologic abnormalities.     

Clinical signs, magnetic resonance imaging features, and outcome after surgical and medical treatment of otogenic intracranial infection in 11 cats and 4 dogs

Brainstem dysfunction resulting from central extension of infection is a life-threatening complication of otitis media/interna (OMI) that has been described infrequently in dogs and cats. We review the clinical signs of disease, diagnostic findings, and results of surgical and medical treatments of brainstem disease attributable to otogenic intracranial infection in cats and dogs. Eleven cats and 4 dogs were examined because of acute, subacute, or chronic clinical signs of brain disease including central vestibular signs, altered mentation, abnormal posture/gait, cranial nerve deficits, and seizures. Results of a minimal database (CBC, serum biochemical panel, urinalysis, thoracic radiographs, and abdominal ultrasonographic images or radiographs) were within reference intervals in all animals. Magnetic resonance (MR) images of the head were acquired for all animals, and cisternal cerebrospinal fluid (CSF) from 9 of 11 cats and 3 of 4 dogs was examined. Surgical exploration and ventral bulla osteotomy were done for 12 of 15 animals, followed by 1–3 months of antibiotic therapy; the remaining animals were euthanized before treatment. In all animals, MR imaging was effective in characterizing the location and extent of the pathologic changes intracranially as well as within middle/inner ear structures. Results of CSF analysis were characteristic of bacterial infection in most of the animals with acute or subacute disease. Since long-term outcome in all treated animals was very good to excellent, it was concluded that dogs and cats with intracranial disease secondary to extension of otitis media/interna have a good-to-excellent prognosis when the condition was diagnosed and was treated by surgical exploration and appropriate antibiotic therapy.     

Diagnostic Features of Clinical Neurologic Feline Infectious Peritonitis

Feline infectious peritonitis (FIP) is a fatal Arthus-type immune response of cats to infection with FIP virus, a mutant of the ubiquitous feline enteric coronavirus (FECV). The disease may occur systemically or in any single organ system, and primary neurologic disease is a common subset of such manifestations. We examined 16 domestic cats with clinical neurologic FIP and 8 control cats with nonneurologic FIP, with the intention of identifying the ante-and postmortem diagnostic tests that most contribute to accurate diagnosis. Of the 16 cats with neurologic FIP, 15 were less than 2 years of age and all 16 originated from large multiplecat households. The most useful antemortem indicators of disease were positive anti-coronavirus IgG titer in cerebrospinal fluid, high serum total protein concentration, and findings on magnetic resonance imaging suggesting periventricular contrast enhancement, ventricular dilatation, and hydrocephalus. Postmortem diagnosis was facilitated by FIP monoclonal antibody staining of affected tissue and coronavirus-specific polymerase chain reaction. Most cats with neurologic and ocular forms of FIP had patchy, focal lesions, suggesting that recently developed technologies described in this report may be useful for evaluation of cats with suspected FIP.     

Feline Temporal Lobe Epilepsy: Review of the Experimental Literature

Accumulating evidence suggests that epileptic seizures originating from the temporal lobe (TL) occur in cats. Typically, affected animals have clinically focal seizures with orofacial automatisms including salivation, facial twitching, lip smacking, chewing, licking, and swallowing. Motor arrest and autonomic and behavioral signs also may occur. Many affected cats have magnetic resonance imaging (MRI) changes within the hippocampus or histopathologically confirmed hippocampal sclerosis or necrosis. From the 1950s to the 1980s, cats frequently were used as animal models for neurophysiological experiments and electrophysiological studies, from which important basic knowledge about epilepsy originated, but which has been rarely cited in clinical veterinary studies. These studies were reviewed. Experimental research on cats showed the widespread anatomical connections among TL structures. The ictal clinical signs originating from the hippocampus, amygdala, or lateral temporal cortex are similar, because of their dense interconnections. The ictal signs can be divided into autonomic, somatic, and behavioral. For research purposes, a 6‐stage system was established, reflecting the usual sequential progression from focal to generalized seizure: attention response (1), arrest (2), salivation, licking (3), facial twitching (4), head turning or nodding (5), and generalized clonic convulsions (6). Knowledge of this data may help in recognizing low‐stage (stage 1 or stage 2) epileptic seizures in clinical practice. Early experimental research data are in accordance with recent clinical observations regarding ictal clinical signs of TL epileptic seizures in cats. Furthermore, the research data supports the idea that TL epilepsy represents a unique clinical entity with a specific seizure type and origin in cats.     

Outcome of ameroid constrictor occlusion of single congenital extrahepatic portosystemic shunts in cats: 12 cases (1993-2000)

OBJECTIVE: To determine postoperative (< or = 6 days), short-term (< or = 90 days), and long-term (> or = 6 months) outcomes of cats undergoing ameroid constrictor occlusion of single congenital extrahepatic portosystemic shunts (PSS) and identify factors associated with outcome. DESIGN: Retrospective study. ANIMALS: 12 cats. PROCEDURE: Cats with single congenital PSS that underwent surgical placement of ameroid constrictors were identified. Follow-up information was obtained through telephone interviews and facsimile correspondence with referring veterinarians and owners. Results-All cats survived the surgery and were discharged from the hospital. One cat had seizures during the postoperative period. Five cats were clinically normal during follow-up evaluations within 90 days after the surgery. Long-term follow-up information was available for 9 cats. Three were clinically normal, 4 had been euthanatized because of progressive neurologic disease, and 2 had neurologic abnormalities that could not be controlled with medication. Four of 7 cats with continued or recurrent neurologic abnormalities 1 or more months after surgery had normal scintigraphic or hepatic function test results 2 to 6 months after surgery. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that the long-term outcome of ameroid constrictor occlusion of PSS in cats is poor. Owners of older cats and cats with preexisting neurologic signs should be made aware of the potential for a poor outcome when considering surgical correction of this disease.     

Central Nervous System Infection Associated With Anaerobic Bacteria in Two Dogs and Two Cats

Central nervous system (CNS) infection caused by anaerobic bacteria (including Bacteroides, Fusobacterium, Peptostreptococcus, and Eubacterium) was diagnosed in two dogs and two cats. In one dog there was extensive meningomyeloencephalitis, presumably the result of hematogenous spread of bacteria from lung abscesses and bacterial endocarditis. Subdural empyema of unknown origin was found in a second dog and two cats. Clinical signs in all four animals included mental depression and focal neurologic deficits, without fever.     

Clinical, cerebrospinal fluid, and histological data from twenty-seven cats with primary inflammatory disease of the central nervous system.

The purpose of this report is to present the clinical, cerebrospinal fluid (CSF) and histological data from 27 cats with inflammatory disease of the central nervous system (CNS). The cats were part of a study of 61 cats admitted to two university clinics over an eight-year period because of signs of CNS disease. The most frequent diseases were feline infectious peritonitis (FIP) (12/27) and suspected viral disease other than FIP (10/27). Typical CSF findings in cats with FIP were a protein concentration of greater than 2 g/L (200 mg/dL) and a white cell count of over 100 cells/microL, which consisted predominantly of neutrophils. In contrast, the CSF of cats with suspected viral disease had a protein concentration of less than 1 g/L (100 mg/dL) and a total white cell count of less than 50 cells/microL. In general, cats with FIP or suspected viral disease were less than four years of age. Neurological signs were usually multifocal in cats with FIP, but focal in cats with suspected viral disease. The CSF findings were variable in five other inflammatory diseases represented. Two cats with protozoan infection had normal CSF total cell counts but abnormal differential counts. The CSF findings were invaluable in differentiating FIP from other causes of inflammatory CNS disease.     

Retrospective analysis of seizures associated with feline infectious peritonitis in cats

Seizures have been reported frequently in feline infectious peritonitis (FIP) but have not been studied in detail in association with this disease. The purpose of this study was to perform a retrospective analysis of neurological signs in a population of 55 cats with a histopathologically confirmed neurological form of FIP. Seizure patterns were determined and it was attempted to relate occurrence of seizures with age, breed, sex and neuropathological features. Fourteen cats had seizure(s), while 41 cats had no history of seizure(s). Generalised tonic-clonic seizures were seen in nine cats; and complex focal seizures were observed in four patients. The exact type of seizure could not be determined in one cat. Status epilepticus was observed in one patient but seizure clusters were not encountered. Occurrence of seizures was not related to age, sex, breed or intensity of the inflammation in the central nervous system. However, seizures were significantly more frequent in animals with marked extension of the inflammatory lesions to the forebrain (P=0.038). Thus, the occurrence of seizures in FIP indicates extensive brain damage and can, therefore, be considered to be an unfavourable prognostic sign.     

Spinal lymphoma in cats: 21 cases (1976-1989).

Medical records of 21 cats with spinal lymphoma were reviewed. All cats were evaluated for neurologic deficits, although 85% of cats necropsied had multicentric disease. Eighty-one percent of cats had hind limb paresis. Results of FeLV tests were positive in 84.2% (16/19) of the cats, and 68.7% (11/16) of the cats had leukemic bone marrow. Spinal lymphoma was confirmed by necropsy in 13 cats, by examination of a biopsy specimen in 1 cat, and by examination of cells aspirated from an epidural lesion in 2 cats. In the remaining 5 cats, a presumptive diagnosis was made on the basis of neurologic examination findings, positive FeLV test results, and leukemic bone marrow. Nine cats were treated with chemotherapy alone. The complete remission rate was 50% in 6 cats given cyclophosphamide, vincristine, and prednisone. The median duration of complete remission was 14 weeks. Complete remissions were not observed in 3 cats given only corticosteroids. A single cat treated by laminectomy and postoperative chemotherapy had a prolonged remission (62 weeks). At necropsy, lymphoma of the CNS was limited to the vertebral canal in 10 of 13 cats; 2 cats had malignant tissue in the brain and vertebral canal, and in the remaining cat, the tumor extended into the brachial plexus. Most tumors extended over multiple vertebral bodies, and 4 cats had more than 1 level of spinal cord involvement. The lymphoma was high-grade lymphoblastic or immunoblastic type in all cats.     

Assessment of the neurologic effects of dietary deficiencies of phenylalanine and tyrosine in cats

OBJECTIVE: To determine the neurologic effects of reduced intake of phenylalanine and tyrosine in black-haired cats. ANIMALS: 53 specific pathogen-free black domestic shorthair cats. PROCEDURE: Cats were fed purified diets containing various concentrations of phenylalanine and tyrosine for < or = 9 months. Blood samples were obtained every 2 months for evaluation of serum aromatic amino acid concentrations. Cats were monitored for changes in hair color and neurologic or behavioral abnormalities. Three cats with neurologic deficits underwent clinical and electrophysiologic investigation; muscle and nerve biopsy specimens were also obtained from these cats. RESULTS: After 6 months, neurologic and behavioral abnormalities including vocalization and abnormal posture and gait were observed in cats that had received diets containing < 16 g of total aromatic amino acid/kg of diet. Electrophysiologic data and results of microscopic examination of muscle and nerve biopsy specimens from 3 cats with neurologic signs were consistent with sensory neuropathy with primary axonal degeneration. Changes in hair color were detected in cats from all groups receiving < 16 g of phenylalanine plus tyrosine/kg of diet. CONCLUSIONS AND CLINICAL RELEVANCE: Findings suggested that chronic dietary restriction of phenylalanine and tyrosine in cats may result in a predominantly sensory neuropathy. In cats, the long-term nutritional requirement for phenylalanine and tyrosine appears to be greater for normal neurologic function than that required in short-term growth experiments. Official present-day recommendations for dietary phenylalanine and tyrosine in cats may be insufficient to support normal long-term neurologic function.     

Analysis of cerebrospinal fluid from the cerebellomedullary and lumbar cisterns of dogs with focal neurologic disease: 145 cases (1985-1987)

Data were obtained from 158 CSF samples from 145 dogs with focal, noninfectious/noninflammatory neurologic disease. The effect of lesion location and the duration and severity of clinical signs were studied. One hundred and twenty-five samples were obtained from the cerebellomedullary cistern (CMC), and 33 were obtained from the lumbar cistern (LC). Intracranial and cervical disease affected the CSF from the CMC more often than did thoracolumbar disease. However, lumbar CSF was more frequently affected by disease anywhere along the neuraxis. For compressive spinal cord disease, the protein concentration at both cisterns was more often high in acute, clinically severe lesions. Intracranial lesions consistently caused abnormalities in CSF from both the CMC (7 of 7; 100%) and LC (2 of 2; 100%). Abnormalities were identified in 16 of 38 (42%) and 5 of 7 (71%) CMC and LC samples, respectively, in dogs with cervical disease. In dogs with thoracolumbar lesions, only 22 of 80 (27.5%) CMC samples were abnormal, compared with 21 of 24 (87.5%) LC samples. These findings suggest that CSF collected cranial to the lesion may be normal or only mildly altered by focal neurologic disease. Fluid obtained caudal to the lesion presumably is more substantially altered because of the predominant caudal flow of CSF. To maximize the yield of diagnostic information from CSF analysis, the fluid should preferably be obtained caudad to the disease site; however, because of problems associated with lumbar puncture, we suggest that CSF from the CMC also be obtained.     

Benign familial juvenile epilepsy in Lagotto Romagnolo dogs

BACKGROUND: Idiopathic childhood epilepsies with benign outcomes are well recognized in human medicine, but are not reported in veterinary literature. We recognized such a neurologic syndrome in Lagotto Romagnolo dogs. ANIMALS: Twenty-five Lagotto Romagnolo puppies from 9 different litters examined because of simple or complex focal seizures and 3 adult Lagotto Romagnolo dogs exhibiting similar clinical signs were used. METHODS: Clinical and diagnostic evaluations of affected dogs were conducted, including electromyography, electroencephalography, and other testing. RESULTS: Seizures in puppies began at 5 to 9 weeks of age and usually resolved spontaneously by 8 to 13 weeks. Those with the most severe seizures also had signs of neurologic disease between these seizures, including generalized ataxia and hypermetria. There were no abnormalities in routine laboratory screenings of blood, urine, and cerebrospinal fluid. Electromyography, brainstem auditory-evoked potentials, and magnetic resonance imaging revealed no specific and consistent abnormalities. Fourteen of 16 (87.5%) affected puppies and 2 of 3 (67%) adult dogs revealed epileptiform activity in the electroencephalogram. Histopathologic examination in 1 puppy and 1 adult dog revealed lesions of Purkinje cell inclusions and vacuolation of their axons restricted to the cerebellum. Pedigree analysis suggests an autosomal recessive mode of inheritance. CONCLUSIONS AND CLINICAL IMPORTANCE: This disorder, with simple or complex focal seizures and cerebellar lesions, represents a newly recognized epileptic syndrome in dogs.     

Necrosis of hippocampus and piriform lobe: clinical and neuropathological findings in two Italian cats

The present paper reports the clinical and neuropathological findings in two cats with a neuropathologically confirmed diagnosis of necrosis of the hippocampus and piriform lobe. The cats were presented because of acute onset of behavioural changes and complex partial seizures. The neurological examination suggested a forebrain lesion. The results of blood examination were within the normal range, and the cerebrospinal fluid (CSF) analysis and computed tomography (CT) scan in one cat did not show any abnormality. Despite therapy with diazepam (Valium; Roche) there was deterioration of the clinical signs and the cats were euthanased. The neuropathological examination revealed hippocampal necrosis that included the piriform lobe.     

Acromegaly in 14 Cats

Acromegaly was diagnosed in 14 middle-aged to old cats of mixed breeding. Thirteen (93%) of the cats were male and one was female. The earliest clinical signs in the 14 cats included polyuria, polydipsia, polyphagia, all of which were associated with untreated diabetes mellitus. All developed severe insulin resistance within a few months; peak insulin dosages required to control severe hyperglycemia ranged from 20 to 130 U per day. Other clinical findings weeks to months after diagnosis included enlargement of one or more organs (e.g., liver, heart, kidneys, and tongue) (n = 14), cardiomyopathy (n = 13), increase in body size and weight gain (n = 8), nephropathy associated with azotemia and clinical signs of renal failure (n = 7), degenerative arthropathy (n = 6), and central nervous system signs (i.e., circling and seizures) caused by enlargement of the pituitary tumor (n = 2). The diagnosis of acromegaly was confirmed by demonstration of extremely high basal serum growth hormone concentrations (22 to 131 micrograms/l) in all cats. Computerized tomography disclosed a mass in the region of the pituitary gland and hypothalamus in five of the six cats in which it was performed. Two cats were treated by cobalt radiotherapy followed by administration of a somatostatin analogue (octreotide), whereas two cats were treated with octreotide alone. Treatment had little to no effect in decreasing serum GH concentrations in any of the cats. Eleven of the 14 cats were euthanized or died four to 42 months (median survival time, 20.5 months) after the onset of acromegaly because of renal failure (n = 2), congestive heart failure (n = 1), concomitant renal failure and congestive heart failure (n = 3), progressive neurologic signs (n = 2), persistent anorexia and lethargy of unknown cause (n = 1), the owner's unwillingness to treat the diabetes mellitus (n = 1), or unknown causes (n = 1). Results of necropsy examination in ten cats revealed a large pituitary acidophil adenoma (n = 10), marked left ventricular and septal hypertrophy (n = 7), dilated cardiomyopathy (n = 1), arthropathy affecting the shoulder, elbow, or stifle (n = 5), and glomerulopathy characterized by expansion of the mesangial matrix and variable periglomerular fibrosis (n = 10).