location of a brain lesion will dictate the associated behavior changes. The limbic system, whose structures lie deep within the brain, functions to control memory, emotions, and basic drives such as sexual activity, anxiety, and feelings of pleasure. Damage to the limbic system can result in personality changes, including increases in fearfulness and aggressive behavior. In other cases, seizures may result. The forebrain, including the prefrontal area, is the part of the brain associated with cognitive behavior, motor planning, thought, and perception. Forebrain lesions can lead to changes in temperament, loss of previously learned behaviors, and failure to recognize or respond appropriately to environmental stimuli. Lesions of the brain stem or forebrain may lead to changes in awareness or consciousness and mentation. Animals with brain stem lesions may demonstrate altered responses to stimuli, dullness, and stupor and may become comatose (Lorenz et al. 2011).
4.6.2.1 Neoplasia
Intracranial neoplasia can be either primary or secondary, and, depending on the location within the brain and the character of the tumor, brain neoplasia can result in several different behavioral changes. Primary brain tumors originate from cells within the brain and meninges and are more likely to result in insidious, slowly progressive effects, whereas secondary tumors resulting from metastatic disease will usually result in acute changes.
Seizures, while the most recognizable, are not always the most common sign of a brain tumor. Other early behavioral and clinical signs of a brain tumor such as changes in behavior and mentation, visual deficits, circling, ataxia, head tilt, and cervical spinal hyperesthesia are often not appreciated. Reluctance to climb stairs, pacing, standing in corners, stumbling over objects, housesoiling, and agitation may also be seen.
4.6.2.1.1 Dogs
Primary brain tumors in the dog may include meningioma, astrocytoma, neuroblastoma, oligodendroglioma, and ependymoma, to name a few. Dogs with brain tumors are usually presented with concurrent neurologic deficits, but one study found that when brain tumors developed in the rostral cerebrum, behavioral changes commonly occurred prior to the appearance of other neurologic deficits (Foster et al. 1998). These changes were described as dementia, aggression, and alteration in established habits. Many of the dogs in the study, but not all, also had seizures, but 72% of them had no neurological deficits on presentation. Neurological deficits eventually appeared in all cases, with some taking up to three months to appear (Foster et al. 1998). Meningiomas, the most common primary brain tumor in dogs, usually occur in dogs more than seven years of age but have been seen in dogs as young as 11 weeks. Behavioral signs may include increases in aggression, head pressing, circling, housesoiling, pacing and panting (common signs of agitation), vocalizations, seizures, and changes in mentation.
While neoplasia in dogs younger than six months occurs less often, the brain is the second most common site for it to develop, so age alone cannot always rule out the possibility of a brain tumor. However, brain tumors occur most often in dogs more than five years of age.
4.6.2.1.2 Cats
Meningiomas are also the most common tumor of the feline brain and have been documented in cats as young as one year of age. Geriatric cats with meningioma have been presented to their veterinarian with the owner complaint of “just not being themselves” (Sessums and Mariani 2009). Clinical signs that have been reported include reluctance to play, episodic lethargy, and aggression. One owner reported apparent pain when she touched her cat’s head, three months prior to presentation with other clinical signs (Karli et al. 2013).
4.6.2.2 Seizures
Generalized seizures in dogs and cats are characterized by the animal falling into a laterally recumbent position with limbs rigid and paddling. They may or may not evacuate their bladder or bowels, they may vocalize, and they will usually fail to respond if spoken to or touched. Focal seizures, however, are involuntary movements that may be localized to a single limb or part of the face. The animal experiencing a focal seizure may be somewhat responsive to other stimuli, but an aura and pre‐ and postictal phases may be present. These types of seizures can result in unusual behavioral presentations and can be difficult to diagnose.
Focal seizures may be divided into motor and sensory‐type seizures. While motor seizures involve involuntary movement of one part of the body, sensory focal seizures may result in abnormal sensations such as tingling, pain, or visual hallucinations. Fly‐biting or fly‐snapping behaviors in some dogs may occur as a result of focal seizures with visual hallucinations. However, evidence linking these and similar behaviors to gastrointestinal distress confirms the possibility of multiple etiologies that can be associated with this non‐specific behavioral sign (Frank 2012; Mills et al. 2020). Complex focal seizures (formerly known as psychomotor seizures) are focal seizures with alterations in awareness. Affected dogs may exhibit repetitive motor activities such as head pressing, vocalizing, or aimless walking or running (Berendt and Gram 1999). In some cases, complex focal seizures manifest as impaired consciousness and bizarre behavior, such as unprovoked aggression or extreme, irrational fear (Dodman et al. 1992, 1996).
Seizures are just one type of involuntary movement disorder in dogs and cats. Other forms of involuntary movements can occur and will need to be differentiated from seizures and primary behavioral disorders. Movements seen during periods of inactivity can be confirmed as movement disorders rather than behavioral disorders. However, involuntary movement disorders such as those associated with cerebellar diseases will occur during periods of activity. Some metabolic diseases and peripheral nervous system and musculoskeletal disorders may also result in involuntary movements. Involuntary movements limited to facial or head movements are likely to be caused by a seizure disorder.
4.6.2.2.1 Cats
Cats with acute onset of partial seizure involving orofacial movements, such as salivation, facial twitching, lip smacking, chewing, licking, or swallowing, along with other behavioral changes, such as sitting and staring while motionless and/or acting confused, have been diagnosed with a form of hippocampal necrosis (Pakozdy et al. 2011). The majority of these cats exhibited other neurological abnormalities on their first presentation. Seizures in cats may also be associated with metabolic disease such as diabetes mellitus, hepatic encephalopathy, neoplasia, or meningoencephalitis (Barnes et al. 2004).
4.6.2.3 Toxicosis
Toxins may lead to personality changes in animals. Animals that have been intoxicated may present with central nervous system signs such as ataxia, stupor, seizures, or death. When signs are acute, a history of exposure is usually present. Shelter staff will be unlikely to encounter these scenarios since once the animal is in the shelter, opportunities to access toxic substances will be limited.
4.6.2.4 Degenerative Conditions
Most degenerative conditions of the neurologic system are heritable and will appear within the first few weeks to months of life. They include such conditions as cerebellar abiotrophy and lysosomal storage diseases.
Cerebellar abiotrophy can be minimal to rapidly progressive and varies to some degree by the breed affected. The condition has been reported in many breeds, including the Kerry blue terrier, rough‐coated collie, beagle, Samoyed, Irish setter, Gordon setter, Airedale, Finnish harrier, Bernese mountain dog, Labrador and golden retriever, cocker spaniel, cairn terrier, and Great Dane. Most puppies will be normal at birth. At two to nine weeks of age, they begin to show signs of cerebellar damage, including ataxia, intention tremors, swaying, hypermetria, a head tilt, and a broad‐based stance. At the extreme, pups may demonstrate opisthotonos with
