Arthropod-Borne Virus Encephalitis

Anthropod vectors transmit viruses that cause encephalitis. In North America the main vector is the mosquito. With West Nile virus humans are secondary hosts while birds are the primary hosts. Arbor virus pertains to specific geographic areas in summer & fall. West Nile and St. Lois are most common and are of Japanese encephalitis serogroup.

Herpes Simplex Virus Encephalitis

Acute inflammatory process of the brain tissue caused by HSV. HSV-1 usually affects children & adults. HSV-2 is more common in neonates (transmitted from infected mother). Initial HSV-1 symptoms include fever, headache, and confusion. Focal neurologic symptoms reflect areas of cerebral inflammation & necrosis: fever, headache, behavioral changes, focal seizures, dysphagia, hemiparesis, and altered LOC

Epilepsy

Group of syndromes characterized by unprovoked, recurring seizures. Syn-dromes are classified by onset, family history, and seizure types. Epilepsy is either primary (idiopathic) or secondary ( underlying cause such as brain tumor).

Meningitis

Inflammation of lining around brain & spinal cord caused by bacteria or viruses. Classified as septic or aseptic.Aseptic: viral or secondary to lymphoma, leukemia, HIV. Strep pneumonia & Niesseria meninigitidis cause 80% of adult meningitis.Septic: bacteria is due to upper respiratory infections, tobacco use, otitis media, and mastoiditis. Bacteria can cross epithelial membrane and enter subarachnoid space.

Creutzfeldt-Jacob Disease & v(CJD)Degenerative & infectious disorder due to ingestion of prions. Prions are smaller than a virus and is resistant to sterilization. The prion lacks nucleic acid, allowing it to withstand sterilization attempts. It crosses the blood-brain barrier & enters tissues where it then produces spongy vacuoles surrounded by amyloid plaque. vCJD onset is 27 years with 22 month survival rate. vCJD includes behavior changes, sensory changes and limb pain, followed by muscle spasm, rigidity, dysarthria, incoordination, cognitive impairment, and sleep disturbances. CJD onset is 50 years with a 6 month survival rate. Symptoms include mental deterioration, ataxia and visual disturbance. As the disease progresses, memory loss, involuntary movement, paralysis, and mutism

Brain Abscess

A collection of infectious material within brain tissue commonly by bacteria. Accounts for <2% of space –occupying brain lesions in US and more common in males during the first two decades of their lives. More common in immunosuppressed due tounderlying disease (otitis media, rhinitis) or immunosuppressive meds.

Seizures

Episodes of abnormal motor, sensory, autonomic, psychic activity , or combination that result from sudden excessive discharge from cerebral neurons. All or part of the brain may be involved. There are 2 types: partial seizures which begin in one part of brain and generalized seizures which involve electrical discharges throughout the whole brainWith Partial seizure, consciousness is intact. Complex partial is impaired consciousness.

Headache (cephalgia)

Headaches are symptoms rather than disease. It indicates organic disease, stress response, vasodilation (migraine), skeletal muscle tension (tension headache), or a combination of factors.

Primary Headache Types: idiopathic, migraine, tension, clusterMigraine Subtypes: Migraine with auraMigraine without auraTension-type (chronic but less severe)Cluster (more severe; 5x > in women)Other primary: triggered by cough, exertion, sexual activity.Cranial arteritis: older population 70+SecondaryOrganic in nature such as brain tumor aneurysm, subarachnoid hemorrhage, stroke, severe hypertension, and head injuries

Multiple Sclerosis

Auto immune-mediated progressive demyelination of CNS. Ages 20-40 and > in women. Sensitized T cells cross blood-brain barrier and remain. The T cells then promote infiltration of other agents that damage the immune system, leading to myelin destruction & oligodendroglial cells. Oligodendroglial cells produce myelin in the CNS