Abstract
Intracranial neoplasia in horses is rare compared to other species. Detailed information such as neurological, electroencephalographic, and histopathological examination of horses with intracranial neoplasia associated with seizures is scarce in the literature. Furthermore, ganglioglioma has not been reported in the horse. A 7-year-old Quarter horse cross Paint gelding was examined due to recurrent seizure-like episodes of 1-year duration. The seizures had been increasing in frequency and length, occurring up to 20 times a day at the time of presentation. Neurological examination revealed intermittent obtundation and multiple left sided abnormalities consisting of upper motor facial and tongue hemiparesis, facial hyperesthesia and cervical hypoesthesia, proprioceptive deficits, thoracic limb hypermetria upon head elevation; and intermittent paroxysmal activity consistent with seizures. Cranial nerve reflexes were normal. Vocalization, conjugate vertical nystagmus, intermittent blindness, left sided head tilt and flexion of neck, and lack of response to environmental stimuli were observed during seizure activity. A right sided cerebrothalamic disease was suspected. An electroencephalogram confirmed seizure activity with main focus on the right side at the central, parietal, and occipital regions further supporting neuroanatomical localization. Additionally, subclinical paroxysmal activity was noted on the electroencephalogram. A ganglioglioma was identified in the right cerebrothalamic area, and other cranial parts of the brainstem based on immunohistochemical examination. To the authors' knowledge this is the first report of intracranial ganglioglioma in the horse. This intracranial neoplasia should be added to the possible causes of intracranial masses and seizures in horses.
Highlights
Immunohistochemistry revealed two populations of apparently neoplastic cells; one subset was immunoreactive to glial fibrillary acidic protein (GFAP) and the other was immunoreactive to synaptophysin (Figure 4)
This report describes in detail for the first time the clinical, laboratory, electroencephalographic, and immunohistochemical findings of a horse with ganglioglioma in the brain
The location of the ganglioglioma in the brain of this horse and development of seizures as the most common clinical presentation are similar features to those reported in other species
Summary
Gangliogliomas in children and young adults most frequently affect the temporal lobe followed by the frontal lobe These tumors occasionally occur in the parietal and occipital lobes, less commonly in the brainstem, and rarely in the ventricles. The horse had paroxysmal activity suggestive of seizures every 10 min. Despite the lack of clinical manifestations, the EEG demonstrated paroxysmal activity consistent with seizures every 10–12 s (Figure 2) followed by facial/ear twitches every 1–5 min. Immunohistochemistry revealed two populations of apparently neoplastic cells; one subset was immunoreactive to glial fibrillary acidic protein (GFAP) and the other was immunoreactive to synaptophysin (Figure 4) These results confirmed the tumor was composed of neoplastic glial and ganglion cells, findings most consistent with a ganglioglioma. A primary glial tumor was excluded due to the presence of atypical large cells with neuronal differentiation that were positive on immunohistochemistry for synaptophysin and negative for GFAP expression
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