Generally, the underlying causes of neurological abnormalities of the head and face are similar whichever nerve (or nucleus) is affected, but, in addition, there are a few conditions that are specific to, or more commonly affect, certain nerves.
The pathophysiological mechanisms that cause seizures are poorly understood. Neurons are excitable tissue constantly held in check. Neurons have a seizure threshold and seizures result when the threshold is lowered and there is imbalance between excitatory and inhibitory mechanisms that favors excitation.
Neurological emergencies are common in small animal practice. As with other body systems, infections, neoplasms, trauma, inflammatory processes, congenital and hereditary diseases all affect the central and peripheral nervous systems causing a range of mild to severe conditions.
Veterinary patients can present for a variety of diseases that impact the neurological system. These patients can require anesthesia for stabilization, diagnostic procedures, or surgical correction of these diseases.
Deciding on a treatment plan for an animal with seizures depends on a number of factors, including the suspected etiologic cause of the seizures, the frequency and severity of the observed seizures, and the financial constraints or intentions of the owner.
Lameness, difficulty walking, and reluctance or inability to rise are common presentations for patients presented to small animal practitioners. Disorders of the central and peripheral nervous systems, spine, long bones, joints, tendons, or musculature can all result in these potential signs.
The vestibular system is responsible for the maintenance of balance and equilibrium in the body, and is comprised of a number of anatomic structures. The semicircular canals are located within the thick petrous temporal bone of the skull, and are composed of three bony canals containing membranous ectoderm structures (semicircular ducts) filled with fluid (endolymph).
The clinical manifestation of excessive and/or hypersynchronous neuronal discharge within the brain; may be manifested as episodic impairment or loss of consciousness, abnormal motor phenomena, psychic or sensory disturbances, or autonomic signs such as salivation, vomiting, urination or defecation. Synonyms – convulsion, ictus, fit.
The vast majority of seizures are self-limiting events, with eventual spontaneous return to resting or baseline neurologic function. However, during status epilepticus, a variety of changes occur within cells and networks of cells that result in a situation where the seizure activity becomes self-sustaining.
Acute paraplegia is a sudden onset of paralysis in the pelvic limbs, and is a common problem in small animal patients. Paraparesis is weakness in the pelvic limbs due to a neurologic cause, and can be quite variable in severity (ambulatory to non-ambulatory).
Neck and back pain are common presenting complaints in veterinary medicine and occur in animals with a variety of signalments. Animals may present with a chronic history of lower-grade discomfort, although acute presentations of moderate to severe pain are common and extremely distressing to owner and pet alike.
A variety of clinical signs may be seen with inflammatory CNS disease, depending on what area of the nervous system is affected. Involvement of the forebrain (cerebral cortex and thalamus) may result in seizures, altered mentation (stupor, coma, delirium, head pressing), vision abnormalities, and compulsive pacing or circling. Involvement of the brainstem (pons and medulla oblongata) may result in altered mentation, cranial nerve deficits (e.g., vestibular dysfunction [head tilt, nystagmus], facial nerve paralysis, swallowing difficulties, tongue paralysis), ataxia, and proprioceptive deficits.