Disseminated protothecosis diagnosed by evaluation of CSF in a dog

A 5-year-old female spayed Shetland Sheepdog Mix dog was evaluated for a history of recent seizure activity, progressive hind limb ataxia, polyuria, and polydipsia and no history of gastrointestinal signs. Physical examination findings included conscious proprioceptive deficits, ataxia, and anterior uveitis along with a hypermature cataract in the right eye. Results of a CBC, serum biochemical profile, urinalysis, and computed tomography scan of the brain were unremarkable. Cerebrospinal fluid (CSF) analysis revealed marked eosinophilic pleocytosis and rare organisms consistent with Prototheca spp within neutrophils and macrophages. On postmortem histologic examination, mononuclear inflammation and numerous intralesional algal organisms, similar to those seen on the cytologic preparation of CSF, were found in the brain, eyes, kidneys, and heart. Abnormalities were not detected on gross and histologic examination of the gastrointestinal tract. Cultures of CSF and subdural/olfactory bulb, but not intestinal tract, yielded growth of Prototheca spp, and PCR analysis and DNA sequencing confirmed the organism as Prototheca zopfii genotype 2. We have reported a rare case of disseminated protothecosis that was diagnosed by evaluation of CSF in a dog presented with neurologic signs and no overt enteric disease. Protothecosis should be considered as a rare cause of seizures, even in the absence of obvious enteric signs, and should be included in the differential diagnosis of eosinophilic pleocytosis.     

Detection of Neospora caninum tachyzoites in cerebrospinal fluid of a dog following prednisone and cyclosporine therapy

Abstract: A 9‐year‐old female spayed Shetland Sheepdog was presented to the Kansas State University Veterinary Medical Teaching Hospital for evaluation following a 3‐week history of left rear limb lameness that had progressed to generalized ataxia. Multifocal or diffuse brain lesions were suspected based on physical examination findings. Cerebrospinal fluid (CSF) contained 52 nucleated cells/μL composed of mixed inflammatory cells. Treatment with prednisone and cyclosporine was initiated based on a presumptive diagnosis of granulomatous meningoencephalitis. Thirteen days later the dog was nonambulatory and mentally obtunded. Repeat CSF analysis revealed 298 nucleated cells/μL with 61% eosinophils. Rare protozoal tachyzoites consistent with Neospora caninum, Toxoplasma gondii, or Sarcocystis spp. were found extracellularly and within macrophages and an eosinophil. Despite cessation of prednisone and cyclosporine therapy and provision of supportive care, the dog died 6 days later. Examination of brain tissue sections revealed multifocally extensive, necrotizing, histiocytic, and lymphoplasmacytic meningoencephalitis with numerous protozoal zoites and cysts. Immunohistochemical analysis of brain tissue using a monoclonal antibody specific for N. caninum confirmed the diagnosis of neosporosis. Similar but less severe lesions were noted in the spinal cord, although organisms were not found. This case emphasizes the value of repeated CSF analysis when therapy is ineffective and the importance of excluding infectious causes of meningoencephalitis before commencement of immunosuppressive therapy.     

Automated flow cytometric cell count and differentiation of canine cerebrospinal fluid cells using the ADVIA 2120

Background: Microscopic cell counts in cerebrospinal fluid (CSF) are time-consuming and prone to imprecision. The recently introduced automated hematology analyzer ADVIA 2120 offers an automated cell count and differential for CSF in the veterinary software mode based on laser light scatter and absorbance measurements. Objectives: The purpose of this study was to evaluate the precision, linearity, and accuracy of the ADVIA 2120 CSF assay. Methods: Sixty-seven CSF samples were analyzed on the ADVIA 2120 and total nucleated cell counts (TNCC) and RBC counts were compared with the hemocytometer results. In 21 samples with TNCC >5/muL, ADVIA 2120 results were compared with 100-300 cell manual differentials performed on cytocentrifuged preparations. Statistical analysis included Spearman's rank correlation, Passing-Bablok regression, and Bland-Altman analysis. Results: Repeatability (intra-assay) coefficients of variation (CVs) ranged from 4.19% to 25.94%. Interassay CVs ranged from 2.56% to 28.67%. Accurate results within 30% were achieved for TNCC up to 4000/muL. Except for low TNCC, deviation from the expected value was higher (TNCC of 8/muL instead of 4/muL). The following correlation coefficients (r) and biases were achieved compared with the reference method: r=.90 and bias 2.3/muL for TNCC; r=.88 and bias 32.0/muL for RBC counts; r=.86 and bias +/-13.4% for mononuclear and polymorphonuclear cell percentages; r=.88 and bias -6.1% for lymphocyte percentage; r=.56 and bias 19.4% for monocyte percentage; and r=.75 and bias -9.7% for neutrophil percentage. Conclusion: Our results demonstrated that the automated ADVIA 2120 CSF assay generally compares well with reference methods although there are some limitations for the automated monocyte count and for samples with only mild pleocytosis.     

Eosinophilic meningomyelitis associated with T‐cell lymphoma in a cat

A 12‐year‐old cat was presented for evaluation of progressive tetraparesis. Magnetic resonance imaging of the cervical spine demonstrated T2‐hyperintensity, and contrast enhancement within the C4–C7 spinal cord, with marked meningeal contrast enhancement and segmental nerve root thickening. Lumbar cerebrospinal fluid contained 407 total nucleated cells/μL, with 99% eosinophils. The cat transiently improved with prednisolone, clindamycin, and ivermectin therapy, but subsequently worsened and was euthanized. Necropsy revealed an asymmetric infiltration predominantly of the white matter, meninges, and nerve roots of the C4–C6 spinal cord segments by an unencapsulated, poorly demarcated neoplasm composed of atypical lymphocytes admixed with eosinophils, causing perivascular hemorrhage and lytic necrosis. The neoplastic cells were immunoreactive for CD3, ultimately confirming T‐cell lymphoma.     

Neoplastic pleocytosis in a dog with metastatic mammary carcinoma and meningeal carcinomatosis

Abstract: A 12‐year‐old female spayed Labrador Retriever was presented with a history of seizures and abnormal vocalization. Approximately 1 year before presentation, multiple mammary cysts had been surgically excised. A mammary mass was noted on physical examination, and 2 separate parenchymal brain lesions were found on imaging studies. Cerebrospinal fluid (CSF) collected from the cisterna magna was analyzed, and abnormalities included moderate pleocytosis with atypical discrete round cells that occasionally formed loose clusters. The dog was euthanized, and on necropsy a primary solid mammary carcinoma was identified as well as multiple metastatic foci in the brain with diffuse meningeal involvement. The cells in the CSF had a morphologic appearance similar to the cells in the primary mammary tumor and in the metastatic tumors in the brain. On immunostaining, cells from the primary mammary tumor, the brain tumors, and the CSF expressed cytokeratin. The CSF cells did not express CD18, CD3, or CD79a. A final diagnosis of mammary carcinoma with brain metastasis and meningeal carcinomatosis was made.     

Choroid plexus carcinoma cells in the cerebrospinal fluid of a Staffordshire Bull Terrier

An 11-year-old female intact Staffordshire Bull Terrier was referred to the Queen's Veterinary School Hospital at the University of Cambridge with sudden onset of episodic behavioral changes, a mammary mass, and papilledema in the right eye. On physical examination the dog appeared depressed and had a head tilt to the right with anisocoria. Using magnetic resonance imaging, a broad-based lesion that obliterated the fourth ventricle was detected in the right brainstem. There was no evidence of pulmonary metastasis. Cerebrospinal fluid (CSF) was then obtained; fluid analysis showed an increased cell count (165 cells/μL, reference interval 0-7 cells/μL) and total protein (0.30 g/L, reference value <0.25 g/L). Cytologic evaluation revealed a population of atypical epithelial cells arranged in cohesive rafts and characterized by moderate to occasionally marked anisocytosis and anisokaryosis. The appearance was highly suspicious of a malignant epithelial neoplasm. The dog was euthanized and on postmortem examination an asymmetrical nonencapsulated cerebellar mass was found within the choroid plexus of the fourth ventricle with local extension into the cerebellopontine angle. Histologic sections of the cerebellar mass contained arborizing papillary structures covered by a single layer of atypical epithelial cells that showed local infiltration into the adjacent neuropil. The diagnosis was choroid plexus carcinoma. The atypical epithelial cells were negative for pancytokeratin and strongly positive for vimentin. The finding of clusters of choroid plexus epithelial cells in the CSF demonstrates the value of utilizing a relatively noninvasive diagnostic technique for diagnosis of choroid plexus tumors.     

Diffuse leptomeningeal histiocytic sarcoma in the cerebrospinal fluid of 2 dogs

Two adult male castrated dogs were evaluated for progressive paraparesis and ataxia. Neurologic examination showed severe ataxia, delayed proprioceptive placement in the pelvic limbs, pain upon palpation of the lumbar spine as well as facial paresis in one dog, and decreased withdrawal reflex of the pelvic limbs in the other dog. Magnetic resonance imaging (MRI) in both dogs showed diffuse meningeal and intramedullary lesions. However, no evidence of a mass was found. Biopsies could not be performed safely due to the location of the lesions. Cerebrospinal fluid (CSF) examination revealed an inflammatory pleocytosis associated with increased protein concentration and numerous large atypical round cells, often multinucleated. Nuclear fragmentation, micronuclei, and rare atypical mitoses were observed. Immunocytochemistry revealed CD1⁺ and CD11c⁺ staining, which, in concert with the morphology confirmed the diagnosis of histiocytic sarcoma (HS). Euthanasia was elected due to poor prognosis. Histopathologic examination showed diffuse spinal and meningeal infiltration with CD18⁺ neoplastic cells, without any evidence of mass formation, which completed the diagnosis of diffuse leptomeningeal HS involving the brain and the spinal cord. Canine central nervous system (CNS) HS has been seldom reported in the literature, with only isolated cases identified on CSF cytology. The cases reported here are remarkable in describing a diffuse CNS leptomeningeal HS associated with neoplastic cells in the CSF of dogs without a tumor mass. These cases emphasize the potential critical importance of CSF analysis in providing an antemortem diagnosis of neoplasia in neurologic patients.