NAVLE Nervous

Canine Nervous System Neoplasia Study Guide

📅 March 28, 2026 ⏱ 25 min read
Nervous system neoplasia represents a significant category of neurological disease in dogs, with intracranial tumors being one of the most common causes of new-onset neurological dysfunction in older dogs.

Overview and Clinical Importance

Nervous system neoplasia represents a significant category of neurological disease in dogs, with intracranial tumors being one of the most common causes of new-onset neurological dysfunction in older dogs. Primary brain tumors account for approximately 2-5% of all canine cancers. Dogs are the only mammalian species besides humans in which spontaneous brain tumors arise frequently.

Approximately 90% of primary brain tumors (PBT) in dogs are represented by meningiomas (approximately 50%), gliomas (approximately 35%), and choroid plexus tumors (CPT; approximately 7%). Understanding the clinical presentation, breed predispositions, diagnostic approach, and treatment options is essential for NAVLE success.

High-YieldFor NAVLE, remember the critical breed predispositions: Brachycephalic breeds (Boxers, Boston Terriers, Bulldogs) are highly predisposed to GLIOMAS. Dolichocephalic breeds (Golden Retrievers, Collies) are predisposed to MENINGIOMAS. Golden Retrievers are also overrepresented for choroid plexus tumors.
Location Definition Common Tumor Types
Extra-axial Originates outside neural parenchyma (meninges) Meningioma, histiocytic sarcoma, lymphoma
Intra-axial Originates within neural parenchyma Gliomas (oligodendroglioma, astrocytoma)
Intraventricular Originates within ventricular system Choroid plexus tumors, ependymoma

Classification of CNS Neoplasia

Intracranial Tumor Classification

Spinal Tumor Classification

NAVLE TipOn myelography, extradural tumors show compression from outside the dura. Intradural-extramedullary tumors create a characteristic 'golf tee' or cup-shaped appearance. Intramedullary tumors cause spinal cord widening.
Category Location Common Types
Extradural Outside dura mater; most common Osteosarcoma, fibrosarcoma, lymphoma, multiple myeloma
Intradural-Extramedullary Within dura but outside spinal cord Meningioma, nerve sheath tumor, nephroblastoma
Intramedullary Within spinal cord parenchyma Astrocytoma, ependymoma, oligodendroglioma

Primary Intracranial Tumors

Meningioma

Meningiomas are the most common primary intracranial tumor in dogs, accounting for approximately 50% of all primary brain tumors. They arise from arachnoid cap cells of the leptomeninges and are typically slow-growing extra-axial masses.

Breed Predisposition and Epidemiology

  • Dolichocephalic breeds: Golden Retrievers, German Shepherds, Collies
  • Other predisposed: Boxers, Miniature Schnauzers, Rat Terriers
  • Median age: 10.5 years
  • No sex predisposition

Clinical Signs

  • Seizures (most common, approximately 50% of cases)
  • Progressive behavioral changes
  • Circling toward side of lesion
  • Visual deficits (contralateral menace deficit)
  • Head pressing, obtundation (increased ICP)

MRI Characteristics

Treatment and Prognosis

Gliomas (Oligodendroglioma and Astrocytoma)

Gliomas are the second most common primary brain tumors in dogs (approximately 35%). They arise from glial cells within brain parenchyma. Oligodendroglioma is more common than astrocytoma in dogs (69% vs 22% of gliomas).

Breed Predisposition and Epidemiology

  • Highly predisposed: Boxer, Boston Terrier, Bulldog (English, French), Bullmastiff
  • Over 50% of all gliomas occur in brachycephalic breeds
  • Genetic locus on canine chromosome 26 associated with susceptibility
  • Median age: 8 years
  • Male predilection: 1.53:1 male to female ratio

Clinical Signs

  • Seizures (most common, especially frontal/temporal involvement)
  • Behavioral changes (aggression, disorientation)
  • Visual deficits
  • Progressive neurological deterioration

MRI Characteristics

Exam Focus: When you see a Boxer or Boston Terrier with new-onset seizures over 5 years old, an intracranial glioma should be high on your differential list. The combination of brachycephalic breed + seizures + progressive neurological signs is classic for glioma.

Choroid Plexus Tumors

Choroid plexus tumors (CPTs) arise from the epithelium of the choroid plexus and account for approximately 7-10% of primary intracranial tumors. They are classified as choroid plexus papilloma (CPP, benign) or choroid plexus carcinoma (CPC, malignant).

Key Features

  • Golden Retrievers: 3.7 times higher risk than expected
  • Median age: 5.5 years (youngest median age among PBT)
  • Over 50% arise from fourth ventricle
  • Clinical signs: Vestibular dysfunction, hydrocephalus, behavioral changes

CPP vs CPC Differentiation

High-YieldCSF protein greater than 80 mg/dL is only seen in choroid plexus carcinoma, never in papilloma. This helps differentiate benign from malignant choroid plexus tumors.
MRI Finding Description
T1-weighted Iso- to mildly hyperintense relative to gray matter
T2-weighted Iso- to slightly hyperintense relative to gray matter
Contrast Enhancement Strong, homogeneous enhancement (characteristic)
Dural Tail Sign Thickening and enhancement of adjacent dura (highly suggestive)
Associated Findings Peritumoral edema, mass effect, calvarial hyperostosis (23%)

Spinal Cord and Vertebral Tumors

Vertebral Tumors (Extradural)

Extradural tumors are the most common spinal tumors in dogs. Primary bone tumors (osteosarcoma most common) and metastatic neoplasia predominate.

Spinal Nephroblastoma

A unique primary intradural-extramedullary tumor with specific predilection for young dogs.

  • Age: Young dogs (5-36 months)
  • Breed: German Shepherds and retrievers overrepresented
  • Location: Consistently T10-L2 spinal cord segments
  • Prognosis: Surgical resection can provide greater than 3 years survival
NAVLE TipWhen you see a young German Shepherd (under 3 years) with progressive paraparesis and an intradural-extramedullary mass at T10-L2, think spinal nephroblastoma. This tumor has a favorable prognosis with surgical resection.
Treatment Median Survival Notes
Surgical Resection 198-2104 days Best for rostral meningiomas; complete resection difficult
Radiation Therapy 130-900 days (median 536) Definitive RT protocols preferred
Palliative (steroids) Weeks to months Prednisone 1 mg/kg/day; reduces edema

Diagnostic Approach

Clinical Assessment

  • Signalment: Age, breed, sex provide differential guidance
  • History: New-onset seizures in dogs greater than 5 years suggests structural disease
  • Neurological exam: Localize lesion to brain region or spinal segment
  • Staging: 3-view thoracic radiographs, abdominal ultrasound

Advanced Imaging

Feature Description
Location Intra-axial; frontal, temporal, parietal lobes
T1-weighted Iso- to hypointense; oligodendrogliomas more T1 hypointense
T2-weighted Hyperintense
Contrast Enhancement Variable; ring enhancement common in high-grade tumors
Oligodendroglioma Smooth margins, contact with ventricles and brain surface

Treatment Options

Palliative Care

Definitive Treatment

  • Surgery: Best for rostral meningiomas; cytoreduction or biopsy
  • Radiation: 2.7-3.0 Gy fractions; best for meningiomas, pituitary tumors, lymphoma
  • Chemotherapy: Limited role; effective for lymphoma, some gliomas
Feature CPP (Papilloma) CPC (Carcinoma)
CSF Protein Median 34 mg/dL (range 32-80) Median 108 mg/dL; greater than 80 only in CPC
MRI Metastases None Drop metastases in 35%

Prognosis Summary

Tumor Type Characteristics Imaging Features
Osteosarcoma Most common; large breeds; thoracic/lumbar Mixed lytic/proliferative; T2 heterogeneity
Multiple Myeloma Plasma cell tumor; multifocal; older dogs Punched-out lytic lesions; homogeneous enhancement
Lymphoma Epidural mass; may extend through vertebrae T2 hyperintense; cortical sparing
Modality Advantages Best For
MRI Gold standard; greater than 90% specificity All intracranial tumors; brainstem/cerebellum
CT Excellent bone detail; faster; more available Vertebral tumors; RT planning
Myelography Shows compression patterns Spinal tumors when MRI unavailable
Drug Dose Purpose
Prednisone 1 mg/kg/day PO, then taper Reduces peritumoral edema
Levetiracetam 20-30 mg/kg PO q8h Seizure control; fewer side effects
Zonisamide 5-10 mg/kg PO q12h Alternative anticonvulsant
Tumor Type Palliative MST Treatment MST Prognosis
Meningioma Weeks-months 12-24 months Most favorable
Glioma 26 days 84-512 days Guarded
Vertebral Tumors Poor Median 135 days Guarded

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