Cancer of the

nervous system In biology, the nervous system is the complex system, highly complex part of an animal that coordinates its behavior, actions and sense, sensory information by transmitting action potential, signals to and from different parts of its body. Th ...

is common in domestic canids, and includes primary neoplasia of the peripheral nervous system, primary neoplasia of the central nervous system and various

metastatic Metastasis is a pathogenic agent's spreading from an initial or primary site to a different or secondary site within the host's body; the term is typically used when referring to metastasis by a cancerous tumor. The newly pathological sites, ...

cancers. Some of the most common of the central nervous system tumors are several types of primary (originating from brain tissue) canine brain tumors. Examples of these include: meningiomas, astrocytomas,

glioblastoma Glioblastoma, previously known as glioblastoma multiforme (GBM), is the most aggressive and most common type of cancer that originates in the brain, and has a very poor prognosis for survival. Initial signs and symptoms of glioblastoma are nons ...

s, oligodendromas, choroid plexus papillomas, and pituitary adenomas. Breeds predisposed to brain tumors include: Boxer Dog, Pug, English Bull Dog, Boston Terrier, and Golden Retrievers.

Common canine brain tumors

Meningiomas

Meningioma Meningioma, also known as meningeal tumor, is typically a slow-growing tumor that forms from the meninges, the membranous layers surrounding the brain and spinal cord. Symptoms depend on the location and occur as a result of the tumor pressing ...

s (arising from the meninges, a neural crest-derived cell) are the most common brain tumor of dogs, accounting for 40% of all primary brain tumors. Golden Retrievers as well as other

dolichocephalic Dolichocephaly (derived from the Ancient Greek δολιχός 'long' and κεφαλή 'head') is a term used to describe a head that is longer than average relative to its width. In humans, scaphocephaly is a form of dolichocephaly. Dolichoceph ...

(long-nosed) breeds are particularly susceptible.

Astrocytomas and glioblastomas

Astrocytoma Astrocytoma is a type of brain tumor. Astrocytomas (also astrocytomata) originate from a specific kind of star-shaped glial cell in the cerebrum called an astrocyte. This type of tumor does not usually spread outside the brain and spinal cord, an ...

s are the most common neuroectodermal tumor of dogs.

Glioblastoma Glioblastoma, previously known as glioblastoma multiforme (GBM), is the most aggressive and most common type of cancer that originates in the brain, and has a very poor prognosis for survival. Initial signs and symptoms of glioblastoma are nons ...

s are considered a subset of astrocytomas—a particularly damaging, invasive, and undifferentiated type. Canine glioblastomas are similar to glioblastomas in humans. Studies are underway to use and develop the dog as a model of this devastating disease of humans in the hope that characterizing and successfully treating these tumors in dogs may lead to improved therapies for humans afflicted with this disease.

brachycephalic Brachycephaly (derived from the Ancient Greek '' βραχύς'', 'short' and '' κεφαλή'', 'head') is the shape of a skull shorter than average in its species. It is perceived as a cosmetically desirable trait in some domesticated dog and ...

(short-nosed) breeds such as the boxer, pug, Boston terrier and bulldog have a marked (25 times the normal occurrence) predilection for developing primary brain tumors to include glioblastomas.

Pituitary gland adenoma

Pituitary gland tumors are very common in the canine. A productive form arising from the anterior pituitary is the primary cause of

Cushing's disease Cushing's disease is one cause of Cushing's syndrome characterised by increased secretion of adrenocorticotropic hormone (ACTH) from the anterior pituitary (secondary hypercortisolism). This is most often as a result of a pituitary adenoma (spec ...

of dogs. This tumor causes excessive production of

cortisol Cortisol is a steroid hormone in the glucocorticoid class of hormones and a stress hormone. When used as medication, it is known as hydrocortisone. Cortisol is produced in many animals, mainly by the ''zona fasciculata'' of the adrenal corte ...

from the

adrenal cortex The adrenal cortex is the outer region and also the largest part of the adrenal gland. It is divided into three separate zones: zona glomerulosa, zona fasciculata and zona reticularis. Each zone is responsible for producing specific hormones. I ...

which leads to the classic signs of alopecia (hair loss), polyuria (excessive urination), polydipsia (excessive water drinking), and a pot-bellied appearance of the abdomen due to muscle break down. See pictur
here

Clinical signs

Two of the most important signs a dog may have an intracranial brain tumor are

seizure A seizure is a sudden, brief disruption of brain activity caused by abnormal, excessive, or synchronous neuronal firing. Depending on the regions of the brain involved, seizures can lead to changes in movement, sensation, behavior, awareness, o ...

and unexplained behavioral changes. Seizures manifest as a 1–2 minute display of a combination of the following: loss of consciousness, lateral recumbency (dog lying on its side), paddling of the legs, tremors, and involuntary urination/defecation. Often, the only signs an absent owner may have of a pet dog that has had a seizure is unexplained soiling of the floor by a normally house-broken pet. Behavioral changes can manifest in many ways to include nervousness, barking in the corner (dementia), pacing, aggressiveness or irritation, or deviation from normal routines. "Doggy headaches" can manifest as

head pressing Head pressing is a veterinary condition characterized by pressing the head against a wall or pushing the face into a corner for no apparent reason. This condition is seen in dogs, cats, Cattle, cows, horses, and goats. Head pressing is usually a ...

against walls, doors, or even owners themselves. Other signs that may be encountered are ataxia (uncoordinated ambulation), circling, blindness, lethargy, and disorientation.

Treatment

At this time, there is no true cure (100% remission) for brain tumors in dogs (or any species for that matter.) In practice, brain tumors are generally considered to be malignant due to the delicate and poorly regenerative nature of neurons and restriction of the brain to the finite space of the cranium which does not allow tumor growth devoid of collateral damage to brain parenchyma. Therefore, general long-term prognosis for canine brain tumors is poor. Current treatment of brain tumors revolves around four main modalities: surgery, radiation, chemotherapy, and palliative (pain relieving) care. Depending on the type, extent, and location of the cancer, any one or combination of these techniques may be employed. For instance, the first line treatment for meningiomas is surgery but may be coupled with chemotherapy in an attempt to improve survival time. Intracranial tumors (such as

) more commonly rely on radiation therapy as surgical access to the tumor may be prohibitively dangerous.Spugnini EP, Thrall DE, Price GS, Sharp NJ, Munana K, Page RL (2000). Primary irradiation of canine intracranial masses. Vet Radiol Ultrasound 41: 377–80. Palliative care tends to include corticosteroids to help reduce swelling and edema around tumors as well as anti-convulsant medications to control seizures.

Notes and references

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Brain tumours A brain tumor (sometimes referred to as brain cancer) occurs when a group of cells within the brain turn cancerous and grow out of control, creating a mass. There are two main types of tumors: malignant (cancerous) tumors and benign (non-cancero ...

Brain tumor