• Scalp protects skull but infection can enter through veins draining the face or through the loose connective tissue layer

• Trauma to skull can produce hematomas or fractures that can let infection enter

• Cerebrospinal fluid protects the brain, but can carry infection

• Meningeal layers can have hemorrhages & hematomas

• Vertebral column can dislocate, fracture, or disks can protrude, which can affect neural function

• Lordosis – exaggerated lumbar curvature• Kyphosis – exaggerated thoracic curvature• Scoliosis – lateral displacement• Discs decrease in size & flexibility with age and can herniate

• Autoregulation of blood flow guarantees adequate blood supply to the brain

• Infarcts occur at margins of adjacent vascular fields that supply the cortex – watershed zones, after impaired perfusion (fibrillation) or oxygenation (CO poisoning, drowning)

• Areas of infarct undergo liquefaction nerosis, leaving a cyst – lacunae

• Vasogenic edema – with inflammation

• Brain tissue swells if capillaries get permeable & allow accumulation of fluid

• Cytotoxic edema – results from hypoxia – intracellular swelling

• Expansion of brain, CSF, blood in the skull can increase intracranial pressure, impair perfusion, compress, shift or tear tissue, herniation can occur

• Compensations include decreased CSF & blood volume, with eventual hypoxia that increase blood pressure, eventually coma & death

• Oversecretion, impaired absorption, blocked circulation of CSF expands the ventricles – hydrocephalus – alleviated by shunting

• Consciousness levels can be measured to assess neural function

• Causes of coma include alcohol or barbiturate overdose, trauma, stroke, epilepsy, meningitis, diabetes, kidney failure, heart disease

• Reflexes & automatic functions aid in localization of CNS lesions

• Neural tube defects can lead to defects in the bone or meninges, abnormal development of tissue - spin bifida in spinal cord, anencephaly in the brain

• Aneurysms are dilation of an artery at an injury or weak side, usually by the circle of Willis – berry or fusiform, or secondary to hypertension – microaneurysms

• Hemorrhage causes violent headaches, blood in the CSF

• Subarachnoid vasospasms happen spontaneously or secondary to subarachnoid hemorrhage

• Arteriovenous malformation are congenital and can cause ischemia and hemorrhage

• Infection or inflammation can cause clots in cerebral veins or venous sinuses

• Usually arise from ear, sinuses, scalp, nasal cavity, or the face

• Cerebrovascular accidents occur when blood flow is impaired by occlusion or hemorrhage – will affect function controlled by the area

• More common in people with hypertension, heart disease, hypercholesterolemia, diabetes, atherosclerosis, oral contraceptive use, smokers

• TIA – brief vasospasm of an artery from a developing plaque but are temporary and reversible

• Amaurosis fugax with TIA in ophthalmic artery

• Thrombotic CVA is from a thrombus on a plaque, usually due to atherosclerosis, asymptomatic until major stenosis blocks flow

• Ischemia is followed by infarct & liquefaction necrosis

• embolic CVA’s are 2nd most common, usually from a-fib, but also from fractures or tumors - they occur more rapidly

• Hemorrhagic CVA can produce a hematoma mass, usually because of hypertension and aneurisms, blood can enter ventricles or subarachnoid space

• Bacterial infection of subarachnoid space – pyogenic meningitis – causes stiff neck, fever, vomiting, + Brudzinski & Kernig signs

• Nisseria meningitides, streptococcus pneumoniae, hemophilus influenzae most common causes

• Other bacteria are syphilis, lyme disease, tuberculosis can affect brain tissue

• Viral infections can cause viral meningitis & fatal encephalitis

• Varicella & measles virus remains in nervous tissue

• Reye’s syndrome is postviral, affects the CNS, seen after aspirin use

• Brain abscesses are treated with antibiotics

• CNS tumors vary between children & adults

• Adult tumors arise in glial cells that still undergo mitosis, secondary metastasis from lung, breast, skin, kidney cancers

• Stem cell tumors usually arise in children

• Drugs that affect autonomic function produce broad or focused effects by blocking or stimulating receptors

• Peripheral nerve injuries can repair, 1.5mm/day; not central lesions because of atrophy and scar tissue

• Peripheral nerve injuries - decreased muscle tone, weakness or paralysis of voluntary movement, loss of reflexes, muscle atrophy

• Upper motor neuron – increased muscle tone, weakness or loss of voluntary movement, increased reflexes, abnormal plantar reflex

• Cerebellar lesions cause tremor, difficulty in performing voluntary movements

• Basal ganglia lesions cause difficulty initiating movement, tremor or other movements at rest, rigidity

• Parkinson disease – from a lesion in the substantia nigra – loss of dopamine - muscle rigidity, bradykinesia, tremor, stooped posture, shuffling gait, autonomic dysfunction

• Huntington disease – dominant inheritance – loss of GABA - motor disorder, cognitive impairment, derangement

• Cerebral palsy – ante or perinatal lesion to a normal nervous system impairs voluntary control, hyperreflexia, symptoms like either basal ganglia or cerebellar dysfunction

• Muscle diseases, usually from genetic or autoimmune disorders, cause muscle weakness

• Myasthenia gravis is a disorder of neuromuscular junction, autoimmune loss of neurotransmitter receptors for acetylcholine

• Acetylcholinesterase inhibitors allow ACh accumulation to counteract loss of receptors

• Multiple sclerosis – sensory, motor, psychic abnormalities from an immune-mediated attack on central nervous system myelin that leaves scars called plaques

• Guillain-Barre syndrome is immune attack of peripheral myelin

• Agents can cause lesions in peripheral nerves

• Viatmin B12 deficiency can affect spinal cord function, and alcoholic degeneration Korsakoff’s psychosis

• Entrapment syndrome cause focal lesions, with weakness & impaired sensations

• Injury to the spinal cord interrupts sensory, motor pathways, with increased reflex activity below the site of the lesion

Amyotrophic lateral sclerosis – loss of corticospinal neurons without any cognitive impairment

• Autosomal recessive disorders:

• Wednig-Hoffmann disease – weakness – floppy baby syndrome

• Wohlfart-Kugelberg-Welander disease - loss of motor supply to proximal muscles

• Friedrech’s Ataxia – thin spinal cord affecting movements

• Alzheimer disease – progressive loss of cortical neurons, degenerative dementia that affects all mental function

• Biopsies show neurofibrillary tangles and neuritic plaques of amyloid

• Seizure – rapidly evolving disturbance of brain function that can produce impaired consciousness, abnormal sensations or mental functioning, or convulsive movements

• Nonepileptic seizures are secondary to conditions like alcohol withdrawal, meningitis, liver or kidney failure

• Epileptic seizures result when a relatively permanent change in the environment, input, or nature of cortical gray matter pyramidal cells allows some of them – the focus – to discharge spontaneously & recruit larger areas

• Pyramidal cells are predisposed to generating seizures

• Most seizures begin focally and produce temporary recruitment that presents as an aura –mental, sensory, or motor phenomena at the onset;, localized EEG activity, abnormal movements, sensations, consciousness, or psychic function

• Prodrome – set of symptoms that warns of an impending seizure

• Partial seizures begin at a limited focus

• Simple partial seizure can spread to become a complex or generalized (secondarily generalized tonic-clonic seizure)

• Complex seizures include an alteration of consciousness, may show automatisms – purposeless behaviors

• Generalized seizures arise instantly with no evidence of focal origin

• Absence seizures – minor impairments of neural function & consciousness

• Tonic-clonic grand mal seizures – begin with prodrome, and have jerks• Normal consciousness depends on sensory stimulation & processing

and integrated function of the reticular activating system, cortex, hippocampus

• Consciousness is unimpaired in simple partial seizures, impaired in partial complex & specific generalized seizures

• Grand mal status epilepticus (tonic-clonic status) is medical emergency

• Acidosis, increased CO2, hypo-glycemia from muscle contraction, can lead to death

• Evaluation of tendency to have seizures involves routine EEG, CT, MRIdrug therapy with a single anticonvulsant is usual medical management