Brain tumors

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Brains tumors are relatively common neoplasias in dogs and can affect the CNS parenchyma, the meninges and the supporting structures of the skull.

Compression of neural structures (mass effect) and nerve destruction are the common pathological sequela which induce clinical symptoms associated with these tumors.

Meningioma are the most common primary brain tumor, followed by lymphoma and gliomas (astrocytoma, oligodendroglioma, glioblastoma multiforme, ependymoma) and choroid plexus papilloma.

Other tumors include neuronal tumors such as neuroblastoma, gangliocytoma, medulloblastoma and microgliomatosis and neuroblastoma.

Secondary brain tumors include round cell tumors such as histiocytoma, peripheral nerve sheath tumor, meningeal sarcomatosis and meningeal carcinomatosis.

Lesion location Possible clinical signs
Cerebrum, thalamus Seizure, behaviour change, altered mental status, circling, pacing, head pressing, head turn, contralateral postural reaction deficits, blindness
Brainstem Altered mental status, circling, head tilt, nystagmus, ataxia, hemiparesis or tetraparesis, postural reaction deficits (contralateral most common, ipsilateral if rostral midbrain), dysphagia, cranial nerve deficits (III-XII possible), irregular respiration
Cerebellum Cerebellar ataxia, truncal ataxia, hypermetria, intention tremors, broad-based stance, ipsilateral menace response deficit with normal vision and palpebral reflex, opisthotonus, vestibular signs

Although X-rays may be informative to help toward a diagnosis, MRI or CT scans are the preferred diagnostic procedures. CSF fluid is often abnormal but frequently non-diagnostic[1]. Tumor location together with imaging characteristics may help to define the most likely differential diagnosis. Intracranial neoplasms are classified as either primary or secondary; primary neoplasia being more common. Definitive diagnosis is based on the results of biopsy, cytology and histopathology.

Treatment involves surgical resection/debulking, radiotherapy and chemotherapy. Although the majority of intracranial tumours are slow growing, they are usually quite advanced by the time of diagnosis and consequently, the prognosis is guarded.

Tumour type Classification Predilection site Pathology Frequency
Angioblastoma Meningeal tumor Variable Solitary Rare
Astrocytoma Glioma Prosencephalon, intra axial Solitary Common
Choroid plexus tumors Neuroepithelial tumor Fourth ventricle Solitary Common
Craniopharyngioma Neurglial tumor Ventricular (3rd ventricle) Solitary, 20 hydrocephalus
Ependymoma Neuroepithelial tumor Third and lateral ventricles Solitary, 20 hydrocephalus Uncommon
Gangliocytoma Nerve cell tumor cerebral hemispheres Solitary Uncommon
Ganglioglioma Nerve cell tumor Cerebrum, brainstem, spinal cord, eye Solitary Uncommon
Ganglioneuroblastoma Nerve cell tumor Cerebrum Solitary Rare
Glioblastoma Nerve cell tumor Cerebrum Solitary Rare
Hamartoma Epithelial tumor None Solitary or multifocal Rare, incidental finding
Hemangioblastoma Neuroaxial tumor brain stem, spinal cord solitary or multiple Rare
Infundibuloma Adnexal tumor Pituitary Solitary Rare
Lymphoma Lymphoid tumor None Solitary or multifocal Common
Malformation tumours (Dermoid sinus, Teratoma, Chiari malformations) Malformations Caudal cranial fossa- 4th ventricle Solitary rare
Medulloblastoma Primitive neuroectodermal tumor Diencephalon Solitary Rare
Medulloepithelioma Primitive neuroectodermal tumor Diencephalon Solitary Rare
Meningioma Meningeal tumor Prosencephalon, spinal cord Solitary or multiple Common
Neuroblastoma Nerve cell tumor Cerebellum, cranial nerve roots, eye, cervical ganglion Solitary Rare
Neurocytoma Nerve cell tumor Cerebellum, spinal cord Solitary Rare
Neurofibrosarcoma Nerve sheath tumor Cerebrum Solitary Rare
Olfactory neuroblastoma Nerve cell tumor Nasal cavity, olfactory, bulb/frontal lobe Solitary; erosion of cribriform plate Rare
Oligodendroglioma Glioma Prosencephalon, intra axial Solitary Rare
Pituitary adenocarcinoma Pituitary tumor Diencephalon Solitary Common
Pituitary adenoma Pituitary tumor Diencephalon Solitary Common
Paraneoplastic disorders Secondary disease Cerebrum, cerebellum Solitary or multifocal Common
Spongioblastoma Glioma Variable, eg, ependymal surfaces, cerebellum, optic nerve and tracts Solitary Rare
Xanthogranuloma Epithelial tumor Thalamus, sella turcica Solitary Rare


  1. Moore, MP et al (1996) Intracranial tumours. Vet Clin North Am Small Anim Pract 26:759