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Central Nervous System CHAPTER 23cns SEEMI USMANI Cerebral Edema     Cerebral edema is the accumulation of excess fluid within the brain parenchyma Can cause an increase in intracranial pressure Vasogenic: extracellular fluid  Integrity of BBB disrupted, fluid escapes into interstitium  Caused...

Central Nervous System CHAPTER 23cns SEEMI USMANI Cerebral Edema     Cerebral edema is the accumulation of excess fluid within the brain parenchyma Can cause an increase in intracranial pressure Vasogenic: extracellular fluid  Integrity of BBB disrupted, fluid escapes into interstitium  Caused by tumors, ischemia, hemorrhage, injury, infections  Results in disturbances in consciousness Cytotoxic: intracellular fluid  Secondary to neuronal membrane injury  Hypoxia-Ischemia- impaired Na/K pump function-cell swelling  Hypo-osmolar states like hyponatremia- fluid shifts into cells by osmosis adu.edu Cerebral Edema In generalized edema the gyri are flattened, and the sulci are narrowed, and the ventricular cavities are compressed adu.edu Hydrocephalus     Hydrocephalus is defined as abnormal increase in CSF within the ventricular system This disorder most often is a consequence of impaired flow, resorption or rarely overproduction of CSF Noncommunicating hydrocephalus- enlargement of part of the ventricular system  Caused by: obstruction- tumor, hemorrhage, inflammation, congenital malformations Communicating hydrocephalus- enlargement of entire ventricular system  Caused by decreased reabsorption by arachnoid villi- block in CSF pathway to the villi, e.g. blood debris, post meningitis scars adu.edu Hydrocephalus      adu.edu Hydrocephalus ex vacuo : A compensatory increase in CSF volume can follow the loss of brain parenchyma as after infarcts or brain atrophy with degenerative diseases Manifestations: If it develops in infancy before closure of suturesenlargement of the head If develops later- increase in I/C pressure- headache, vomiting, papilledema, may cause herniations Intracranial Pressure (ICP)       The brain tissue, blood & CSF in the rigid confines of skull contribute to intracranial pressure ( normal 0-15mmHg) Rise in I/C pressure mainly buffered by changes in volume of CSF Causes of raised I/C pressure- mass effect Brain tumor, abscess, hemorrhage, edema Increased CSF- obstruction to outflow Increased venous pressure- e.g. venous sinus thrombosis adu.edu ICP is pressure exerted by tissue & fluid volumes of the three compartments within the rigid skull Porths pathophysiology 10% 10% adu.edu 80%  Effects of raised ICP:  Decrease in Cerebral Perfusion Pressure or CPP (CPP= MAPICP)- CPP is 70 to 100mmHg Decrease in cerebral perfusion- neuronal death may occur Decrease in level of consciousness is an early sign of raised ICP – confusion to stupor to coma Herniations Cushing triad- late sign, triggered by ischemia of VMC in an attempt to increase CPP  Progressively increasing systolic BP, progressively decreasing diastolic BP ( widening of pulse pressure), bradycardia  Important indicator of raised ICP & cerebral ischemia     adu.edu Herniation        When the volume of tissue, CSF, or blood increases- intracranial pressure rises Rise in intracranial pressure leads to herniation of brain tissue There are three main types of herniation: Cingulate (subfalcine) herniation: Herniation of cingulate gyrus under the edge of falx cerebri, caused by an asymmetric expansion of a cerebral hemisphere May be associated with compression of the anterior cerebral artery Will eventually compromise vital centers in the medulla adu.edu Herniation         Transtentorial herniation: Medial aspect of the temporal lobe herniating into tentorial notch  Pressure on midbrain: III cranial nerve is compromised -ipsilateral pupil dilation The posterior cerebral artery may be compressed, resulting in ischemic injury to visual cortex Pressure on opposite side cerebral peduncle of midbrain- hemiparesis ipsilateral to herniation Later coma, FDPs & respiratory arrest Tonsillar herniation: Displacement of the cerebellar tonsils through the foramen magnum Is life-threatening- causes brain stem compression and damage to the cardio-respiratory centers in the medulla- respiratory & cardiac arrest adu.edu CEREBROVASCULAR DISEASES      Are brain disorders caused by pathologic processes involving blood vessels Three main pathogenic mechanisms are (1) thrombotic occlusion, (2) embolic occlusion, and (3) vascular rupture Stroke is the clinical term for acute-onset neurologic deficits resulting from hemorrhagic or obstructive vascular lesions Thrombosis and embolism result in infarction of regions supplied by the affected vessel Hemorrhage due to rupture of vessels- leads to direct tissue damage as well as secondary ischemic injury adu.edu Global Cerebral Ischemia  Ischemia, due to tissue hypoperfusion can be caused by hypotension, vascular obstruction, or both  Widespread ischemic-hypoxic injury can occur in the setting of severe systemic hypotension (usually when systolic pressures fall below 50 mm Hg), as in cardiac arrest, shock With mild injury- a transient confusional state with complete recovery In severe global cerebral ischemia, widespread neuronal death In those who survive- persistent vegetative state or brain death    adu.edu Focal Cerebral Ischemia Cerebral arterial occlusion leading to focal ischemia and infarction in the distribution of the blocked vessel  Ischemic Stroke :  Embolic occlusions:  Are more common than infarctions due to thrombosis  Causes:  Cardiac mural thrombi (recent MI, ventricular aneurysm)  Atrial fibrillation, valvular disease (bacterial endocarditis)  Emboli from atheromatous plaques within the carotid arteries  Emboli from DVT may cross over to the arterial circulation through cardiac defects and lodge in the brain (paradoxical embolism)  Territory supplied by middle cerebral artery most frequently affected by embolic infarction adu.edu  Ischemic Stroke       Thrombotic occlusions: Usually are superimposed on atherosclerotic plaques Common sites: carotid bifurcation, the origin of middle cerebral artery, and at either end of the basilar artery There may be thrombus fragmentation and distal embolization Focal symptoms depend on vessel involved These nonhemorrhagic infarcts resulting from acute vascular occlusions can be treated with thrombolytic therapy- saves ischemic but viable tissue around necrotic tissue adu.edu      Transient ischemic attacks ( TIAs): Are focal ischemic neurological deficits (without infarction) that last for less than 24h( mostly 1-2h) “brain angina” – temporary ischemia, reverses before infarction occurs Caused by emboli, atherosclerotic disease TIAs provide a warning of impending stroke- timely intervention may prevent a stroke adu.edu Hemorrhagic stroke        Is caused by rupture of a blood vessel & hemorrhage into the brain tissue Causes: Hypertension: causes accelerated atherosclerosis, and small vessel disease- hyaline arteriolosclerosis of deep penetrating arteries & arterioles Rupture of an aneurysm, AVMs Sudden event, associated with a high morbidity & mortality Focal symptoms depend on vessel involved Hemorrhage & resultant cerebral edema- raise intracranial pressure- severe headache, coma & death adu.edu Stroke         Manifestations of Acute Stroke: The acute manifestations depend on blood vessel involved Symptoms are sudden in onset, focal & unilateral There may be weakness of face, arm, or leg, numbness, monocular vision loss, speech disturbances (dysarthria), language disturbance (aphasia) In case of TIAs symptoms resolve spontaneously Diagnosis: CT scan, MRI, Arteriography Treatment: I/V thrombolytic treatment ( tPA) in selected patients adu.edu Intracranial Hemorrhage       Hemorrhages within the brain are associated with: (1) hypertension and other diseases leading to vascular wall injury (2) structural lesions such as arteriovenous malformations (3) tumors Subarachnoid hemorrhages most commonly are caused by ruptured aneurysms Subdural or epidural hemorrhages usually are associated with trauma adu.edu Primary Brain Parenchymal Hemorrhage      Spontaneous (nontraumatic) intraparenchymal hemorrhages are most common in mid- late adult life Most are due to the rupture of a small intraparenchymal vessel Hypertension is the leading underlying cause Can be devastating when it affects large parts of the brain, or extends into the ventricles- or it can affect small regions and be clinically silent Typically occur in the basal ganglia, thalamus, pons, and cerebellum Massive hypertensive hemorrhage rupturing into a lateral ventricle. adu.edu Subarachnoid Hemorrhage- Saccular (berry) aneurysms     The most frequent cause of non-traumatic subarachnoid hemorrhage is rupture of a saccular (berry) aneurysm Subarachnoid hemorrhage may also result from: vascular malformations, rupture of intracerebral hemorrhage into ventricles, hematologic disturbances, tumors Berry aneurysm develop over time due to underlying defects in the vessel media There is an increased risk of aneurysms in patients with ADPKD & in those with genetic disorders of ECM adu.edu About 90% of saccular aneurysms occur in the anterior circulation near major arterial branch points Saccular (berry) aneurysms      Probability of rupture increases with sizeaneurysms larger than 1 cm in diameter have a roughly 50% risk of bleeding/ year Rupture is associated with acute increase in intracranial pressure- patient develops sudden, excruciating headache & rapidly loses consciousness Risk of ischemic injury from vasospasm of other vessels Healing and meningeal scarring may obstruct CSF flow leading to hydrocephalus Other types of cranial aneurysms; mycotic, traumatic, dissecting, atherosclerotic adu.edu Vascular Malformations     Arteriovenous malformations (AVMs) are the most common vascular malformations AVMs, can rupture & are dangerous- affect males more frequently- manifest between10 and 30 years with seizures, an intracerebral hemorrhage (causing hemorrhagic stroke) or a subarachnoid hemorrhage Shunting of blood from arterial to low pressure venous system- rupture a AVMs; tangled network of arteries & veins adu.edu CNS Trauma     A blow to the head may be penetrating or blunt; it may cause an open or a closed injury Head injury can be injury to skull, brain, both When the brain is damaged, the injuries may involve the parenchyma, the vasculature, or both Repetitive trauma (in athletes in contact sports) can lead to later development of neurodegenerative processes Contusions seen in temporal lobes adu.edu Traumatic Parenchymal Injuries   Concussion: momentary interruption of brain function with or without loss of consciousness  Caused by mild head injury- brain imaging negative  Recovery within 24 h- post concussion syndrome  Repetitive mild injury- chronic traumatic encephalopathy Diffuse axonal injury:  The movement of one region of brain relative to another- angular acceleration  Stretching, tearing of axons in white matter of cerebral hemispheres, corpus collosum, brain stem  May lead to coma, death  Most common cause for vegetative state adu.edu Traumatic Parenchymal Injuries        Contusions: A contusion is caused by rapid tissue displacement, disruption of vascular channels, with subsequent hemorrhage, tissue injury, and edema Coup- contrecoup injuries- contusions at the point of impact & on the opposite side of brain due to rebound Contusions mainly seen in frontal & temporal lobes- may involve apices of gyri only , or deeper tissues Can cause mass effects from edema- increased ICP Lacerations: penetration of the brain by a bullet or displaced fracture of skulltissue tearing, vascular disruption, and hemorrhage adu.edu Traumatic Vascular Injury     CNS trauma disrupts vessel walls, leading to hemorrhage Depending on the affected vessel, the hemorrhage may be epidural, subdural, subarachnoid, or intraparenchymal Raise I/C pressure- leading to herniations Intracerebral Hematoma: Within the brain parenchyma caused by acceleration forces or contusions may coalesce  More common in frontal & temporal lobes  Signs symptoms depend on the location adu.edu  Epidural Hematoma      Almost always caused by skull fractures- especially causing rupture of the middle meningeal artery In infants, traumatic displacement of easily deformable skull may tear a vessel, even in the absence of a skull fracture Blood accumulating under arterial pressure from the torn vessel dissects the dura away from the inner skull surface, producing a hematoma that causes rapid compression of brain Typically, unconsciousness followed by a lucid interval for several hours then unconsciousness Constitutes a neurosurgical emergency necessitating prompt drainage and repair to prevent death adu.edu Subdural hematoma       Rapid movement of the brain during trauma can tear the bridging veins passing through the subarachnoid and subdural space to the dural sinuses Produces subdural hematomas- most commonly over the lateral aspects of the cerebral hemispheres In patients with brain atrophy, the bridging veins are stretched out, accounting for the higher rate of subdural hematomas in elderly persons Acute presentation: manifest acutely within the first 48 hours after injury- raised ICP Subdural hematomas organize by lysis of the clot, & growth of granulation tissue Chronic subdural hematomas: subdural hematomas commonly rebleed from the thin-walled vessels of the granulation tissuemay manifest clinically later adu.edu Infections          Meningitis: is an inflammatory process involving the leptomeninges within the subarachnoid space If the infection spreads into the underlying brain it is termed meningoencephalitis Bacterial ( acute pyogenic) meningitis: Causative organisms: Strep. Pneumoniae, N. Meningitides In neonates E.coli, & group B streptococci Risk factors: sepsis, basilar skull fractures, mastoiditis, neurosurgery Purulent exudate in CSF, meninges thicken- adhesions- may impair CSF flow- hydrocephalus Clinically- due to meningeal irritation and neurologic impairment - headache, neck stiffness, photophobia, vomiting, seizures, cranial nerve palsies Systemic signs of infection- fever adu.edu Infections        Dx: Lumbar puncture for CSF examination – high neutrophil count with elevated protein, and reduced glucose CSF- culture Treatment: Antibiotics, corticosteroids Brain Abscesses: Bacterial meningitis may be associated with abscesses in the brain Abscesses are destructive lesions, and patients present with focal deficits as well as general Pyogenic meningitis- a thick signs related to increased intracranial layer of suppurative exudate pressure- and progressive herniation covers the brain stem and cerebellum adu.edu Aseptic Meningitis (Viral Meningitis)           Aseptic meningitis is believed to be of viral origin in most cases, but it is often difficult to identify the responsible virus Characterized by an acute onset of meningeal irritation, fever, and alterations in consciousness Examination of the CSF: shows lymphocytosis, moderate protein elevation, and a normal glucose level The clinical course is less fulminant than in pyogenic meningitistypically self-limiting Encephalitis: Viral encephalitis is a parenchymal infection of the brain- invariably associated with meningeal inflammation (meningoencephalitis) Arboviral infections: Eastern and Western equine encephalitis and West Nile virus infection Herpesvirus infections Clinically same as meningitis, with focal neurological disturbances Other viral infections- rabies virus, poliovirus, HIV adu.edu Tuberculous Meningitis     Tuberculous meningitis caused by Mycobacterium tuberculosis usually manifests with generalized signs and symptoms of headache, malaise, mental confusion, and vomiting CSF: mononuclear cells or a mixture of polymorphonuclear and mononuclear cells; high protein level, and glucose reduced May result in a well-circumscribed intraparenchymal mass (tuberculoma) Chronic tuberculous meningitis leads to arachnoid fibrosis and hydrocephalus from interference with resorption of CSF adu.edu Diseases of Myelin     Include: Demyelinating diseases: of the CNS are acquired conditions characterized by preferential damage to previously normal myelin Most commonly from immune-mediated injury, such as multiple sclerosis (MS) Dysmyelinating diseases: or leukodystrophies; myelin is not formed properly caused by mutations disrupting the function of proteins required for the formation of normal myelin sheaths adu.edu Multiple Sclerosis       MS is an autoimmune demyelinating disorder characterized by episodes of neurologic deficits, separated in time, attributable to white matter lesions that are separated in space Prevalence of approximately 1 per 1000 persons in most of the United States and Europe The disease may become clinically apparent at any age, although onset in childhood or after age 50 is relatively rare Women are affected twice as often as men In most patients with MS, the illness shows relapsing and remitting episodes of neurologic impairment The frequency of relapses tends to decrease during the course of the illness adu.edu Multiple Sclerosis- pathogenesis        MS is an immune mediated disease caused by a combination of environmental and genetic factors- resulting in a loss of self tolerance to myelin antigens Initiating agent, may be an infectious agent Genetic factors: increased risk in first-degree relatives, high concordance rate for twins Increased risk with HLA-DRB1 variants Genetic polymorphisms in the genes encoding receptors for IL-2 and IL-7 A central role for CD4+ T cells has been suggested, with an increase in TH17 and TH1 CD4+- also contributions from CD8+ T cells and B cells Primarily a demyelination- some injury to axons does occur, even leading to neuronal death adu.edu Multiple Sclerosis       Morphology: Multiple, well-circumscribed, slightly depressed, graytan, irregular plaques in the white matter of CNS Plaques frequent in the optic nerves, chiasm, brain stem, around ventricles, ascending & descending fiber tracts, cerebellum & spinal cord Active plaque: show ongoing myelin breakdown, lymphocytes and macrophages Inactive plaques: no inflammation, instead gliosis prominent CSF shows an increased IgG levels- can be used as markers of disease activity  adu.edu a plaque around occipital horn of the lateral ventricle. Multiple Sclerosis           Clinical Features A disease of young adults, 20-45 y, commoner in females The course of MS is commonly one of relapses followed by remissions Can manifest as a variety of symptoms, depending on the location of lesions: Common presentation is acute onset of visual disturbances, loss of vision, parasthesiae, fatigue Abnormal gait, vertigo, speech disturbances, bladder & sexual dysfunction Mood swings, depression, euphoria Changes in cognitive function can be present Recovery during remissions is not complete- leading to a gradual accumulation of neurologic deficits Diagnosis: requires evidence of CNS lesions, in different parts of CNS at least 3months apart on MRI adu.edu Leukodystrophies      Leukodystrophies are genetic disorders caused by mutations of genes involved in myelin production or turnover Some of these mutations affect lysosomal enzymes, while others involve peroxisomal enzymes; a few are associated with mutations in myelin proteins Most are of autosomal recessive inheritance There is progressive involvement of the white matter, with the loss of white matter, the brain becomes atrophic, the ventricles enlarge Present with an insidious and progressive loss of function, often beginning at a younger age; with deterioration in motor skills, spasticity, hypotonia, ataxia adu.edu NEURODEGENERATIVE DISEASES    Degenerative diseases of the CNS are disorders characterized by the degeneration of subsets of neurons typically related by function Many of these disorders are associated with the accumulation of abnormal proteins Clinical manifestations of degenerative diseases are dictated by the pattern of neuronal dysfunction adu.edu Alzheimer Disease          Alzheimer disease is the commonest cause of dementia (a syndrome of intellectual deterioration severe enough to interfere with occupational & social performance) Risk increases with age, the prevalence almost doubles for every 5y beyond 65y of age Most cases of AD are sporadic, but at least 5% to 10% are familial Pathogenesis: Aß peptide derived from APP ( amyloid precursor protein) is associated with pathogenesis of AD APP gene is located on chromosome 21 Large deposits of Aβ lead to formation of plaques- leading to neuronal death & local inflammation Accumulation within cells -neurofibrillary tangles- alter neurotransmission Tau aggregates adu.edu Aβ peptide genesis and consequences in Alzheimer disease    adu.edu Amyloid precursor protein ( APP) cleavage by α-secretase and γsecretase produces a harmless soluble peptide APP cleavage by βamyloid–converting enzyme (BACE) and γsecretase releases Aβ peptide, Aβ peptide forms pathogenic aggregates and contributes to the characteristic plaques and tangles of Alzheimer disease Alzheimer Disease     Cortical atrophy seen, with widening of sulci; most pronounced in the frontal, temporal, and parietal lobes hydrocephalus ex vacuo plaques (extracellular lesions) and neurofibrillary tangles(intracellular lesions) Evident in the medial temporal lobe, hippocampus, neocortex adu.edu Plaques (arrow) contain a central core of amyloid and a surrounding region of Alzheimer disease      Clinical Features: First stage (2-4y): short-term memory loss, changes in personality, impaired higher intellectual function Second stage may last several years- disorientation, lack of insight, impaired problem solving, memory loss, and aphasia Third stage: (lasts1-2y) patient becomes profoundly disabled, mute, and immobile Dx: A diagnosis of exclusion, no tests for disease adu.edu Frontotemporal Lobar Degeneration       FTLDs are a heterogeneous set of disorders associated with focal degeneration and atrophy of frontal and/or temporal lobes They are distinguished from AD in that alterations in personality, behavior and language (aphasias) precede memory loss Frontal lobe involvement leads to behavioral changes, temporal lobe involvement causes, language problems There are heritable forms as well as sporadic cases Pathogenesis: many variants contain tau inclusions within neurons A well known variant Pick disease, is associated with smooth, round inclusions of tau known as Pick bodies adu.edu Parkinson Disease        Is a degenerative disorder of the basal ganglia , resulting in variable combinations of tremor, rigidity, bradykinesia It is caused by dopamine depletion resulting from degeneration of dopamine producing neurons of substantia nigra & nigrostriatal pathway Begins after 50y & presents at 6th to 7th decade Most cases are sporadic, inherited forms exist- which show mutations of α-synuclein gene – a protein involved in synaptic transmission Even in sporadic forms the Lewy bodies are seen—inclusions containing α-synuclein Lewy bodies are seen in the substantia nigra, medulla, pons, eventually in the cerebral cortex and subcortical areas Parkinsonism can be due to: postencephalitic parkinsonism, dopamine antagonist drugs, CVA, tumors, repeated head trauma adu.edu Parkinson Disease    Morphology: Pallor of the substantia nigra due to loss of pigmented, dopaminergic neurons Lewy bodies may be found in neurons that remain in of substantia nigra & other regions of brain Normal substantia nigra adu.edu Pallor of substantia nigra Lewy body Parkinson Disease         Clinical Features: Tremors: of hands & feet, head, neck, face, lips -pill rolling movements at rest decrease with movement Rigidity: resistance to movement during passive joint movement- cog-wheel rigidity Bradykinesia: slowness in initiating & performing movements, difficulty in unexpected stopping of movements Effects walking, turning, have a shuffling gait, mask-like face, slow monotonous speech, tendency to fall Autonomic manifestations Dementia: late development in 20 % Treatment: Drugs that improve function of dopaminergic system e.g. L-Dopa adu.edu Huntington Disease     Is an autosomal dominant movement disorder associated with degeneration of the striatum (caudate and putamen) Pathogenesis: caused by CAG trinucleotide repeat expansions in a gene located on 4p that encodes protein huntingtin The mutant protein undergoes proteolysis, yielding fragments that can form large intranuclear aggregates Resultant neuronal loss leads to degeneration in the striatum leading to involuntary choreiform movements and cortical neuronal loss leading to severe dementia adu.edu Amyotrophic lateral sclerosis          Affects motor function- degeneration & death of UMNs in cerebral cortex & LMNs in ventral horn cells & motor nuclei in brain stem Sensory system remains intact Presents in 5th decade of life- more common in men, 10% cases familial, rest sporadic Progressive disease Clinically: common presentation is progressive weakness & atrophy of distal muscles of one upper limb UMN damage- paresis, hyperreflexia, spasticity LMN damage- fasciculations, weakness, denervation atrophy, hyporeflexia Later muscles of palate, pharynx, tongue- dysphagia, dysarthria due to involvement of cranial motor nuclei Death from involvement of respiratory muscles, & cranial nerve nuclei adu.edu Congenital Malformations      The incidence of CNS malformations, giving rise to mental retardation, cerebral palsy, or neural tube defects, is estimated at 1% to 2% Genetic factors: Mutations of genes that regulate the differentiation, maturation, or intercellular communication of neurons Environmental factors: Teratogenic effects of various chemicals and infectious agents adu.edu Neural Tube Defects        Failure of the neural tube to close (normally complete by day 28 of embryonic development ) leads to malformations involving some combination of neural tissue, meninges, and overlying bone or soft tissues Most commonly involve the spinal cord Spinal dysraphism or spina bifida: may be bony defect (spina bifida occulta) or more severe malformation with a disorganized segment of spinal cord Meningocele: when there is only a meningeal extrusion Meningomyelocele: most commonly occurs in the lumbosacral region Leads to motor and sensory deficits in the lower extremities & disturbances of bowel and bladder control Encephalocele: a diverticulum of brain tissue extending through a defect in the cranium, most commonly in the posterior fossa adu.edu Neural Tube Defects        Pathogenesis: Genetic: High concordance rate among monozygotic twins Recurrence rate of 4% to 5% in subsequent pregnancies Environmental: Folate deficiency during the first few weeks of gestation is a risk factor Risk related to polymorphisms in enzymes involved in folic acid metabolism adu.edu Other Congenital Malformations         Forebrain Anomalies: Microencephaly: associated with chromosome abnormalities, fetal alcohol syndrome, and HIV infection; caused by a reduction in the number of neurons that reach the neocortex leading to a simplification of the gyral folding Agenesis of the corpus callosum Posterior Fossa Anomalies: Arnold-Chiari malformation type II: a small posterior fossa, with a misshapen cerebellum & downward extension of cerebellar vermis through the foramen magnum Chiari malformation type I: less severe , which low-lying cerebellar tonsils extend down into the vertebral canal- may become symptomatic because of impaired CSF flow and medullary compression Dandy-Walker malformation: an enlarged posterior fossa The cerebellar vermis is absent, in its place is a large midline cyst representing the expanded, roofless fourth ventricle adu.edu Brain Tumors  Primary tumors include:  Glial tumors    Menigiomas  Medulloblastoma  Primary CNS lymphoma Metastatic tumors Focal disturbances:  Dysfunction of particular brain areas  Seizures, hallucinations, weakness or palsies in specific areas, sensory deficits Generalized disturbances  Due to increased intracranial pressure     Astrocytomas Oligodendrogliomas Ependymomas adu.edu Brain Tumors       Tumors of CNS have unique characteristics that set them apart from tumors elsewhere in the body: These tumors do not have detectable in situ stages Even low grade lesions infiltrate large areas of brain- non resectability and poor prognosis Also, any CNS tumor, may have lethal consequences if situated in a critical brain region; e.g. a benign meningioma may cause cardiorespiratory arrest if situated in the posterior fossa Even the most highly malignant tumors rarely metastasize outside the CNS Tumors can spread through the CSF- and thus may be associated with implantation along the brain and spinal cord adu.edu Seizure Disorders    Seizures are paroxysmal motor, sensory, or cognitive manifestations of spontaneous abnormal electrical discharges from collections of neurons in the cerebral cortex Convulsion is a motor seizures involving the entire body Provoked seizures –symptomatic or secondary   Febrile, tumor, infection, vascular lesions, brain injury, hypocalcemia, hypoglycemia Unprovoked seizures – idiopathic, no identifiable cause –epileptic (recurrent seizures) adu.edu The Epileptic Seizures Focal seizures- begins in a focal area of one cerebral hemisphere- most common type  Focal seizures without impairment of consciousnessMotor symptoms, sensory symptoms, autonomic signs  Focal seizures with impairment of consciousness- spread to involve both hemispheres Automatisms, hallucinations, déjà vu Generalized seizures- begin with involvement of both hemispheres, most common in young children Involve unconsciousness & varying degrees of bilateral motor responses Tonic clonic (grand mal seizures) Absence seizures (petit mal seizures)  adu.edu Generalized Convulsive Status Epilepticus      Seizures that do not stop spontaneously or occur in succession without recovery Tonic-clonic status epilepticus may lead to respiratory failure & death May occur as the first manifestation of epilepsy May be caused by neurologic or systemic disease as symptomatic seizures Treated with life support measures & control of seizures adu.edu Acute Spinal Cord Injury    Most injuries that damage the cord are associated with the transient or permanent displacement of the vertebral column The level of cord injury determines the extent of the neurologic manifestations Damage at the region of impact to descending and ascending white matter tracts isolates the distal spinal cord from the rest of the brain adu.edu Acute Spinal Cord Injury      Sudden, complete transection of spinal cord results in complete loss of motor, sensory, reflex, autonomic functions below the level of injury Spinal shock: flaccid paralysis, loss of tendon reflexes, absence of sensations below the level of injury with loss of bowel & bladder function-with hypotension caused by loss of sympathetic tone & vasodilation The higher the level of injury the greater the effect Flaccid paralysis during spinal shock whether lesion is UMN or LMN After period of spinal shock in an UMN injury reflexes & muscle tone return- causing hypertonia & reflex spastic movements which are involuntary adu.edu Types of Spinal Cord Injury  Motor & somatosensory function loss will depend on the level of injury    Quadriplegia-damage in cervical segments; those above C4 can, in addition, lead to respiratory compromise from paralysis of the diaphragm Paraplegia- Lesions involving the thoracic segments or below can lead to paraplegia According to extent of neurologic damage:     adu.edu Complete: No motor or sensory function preserved in sacral segments S4-S5 (ASIA scale A) Caused by severance of cord, interruption of blood supply Incomplete: Some residual motor or sensory function below the level of injury ( ASIA scales B to E) May manifest as certain syndromes Incomplete injury      Anterior adu.edu cord syndrome Anterior cord syndrome: damage to anterior section of cord Damage to anterior spinal artery, causing infarction of anterior 2/3 of cord Loss of motor function –damage to corticospinal tracts Loss of pain & temperaturedamage to lat. spinothalamic tract Fine touch and proprioception preserved Porth’s pathophysiology Incomplete injury           Brown-Sequard syndrome: damage to one hemisection of the cord Motor function, lost on same side Fine touch and proprioception on same side pain/temperature sensation lost from contralateral side Central cord syndrome: injury to central gray/white matter- occurs in cervical cord Arms more affected than legs Conus medullaris syndrome: Flaccid bowell & bladder, altered sexual function, motor function of legs and feet Cauda equina syndrome: LMN type asymmetric flaccid paralysis with sensory impairment adu.edu Porth’s pathophysiology Disruption of Autonomic Nervous System Function in SCI      Affects ANS function below the level of injury; includes sympathetic output from thoracolumbar cord (T1-L2) & parasympathetic from sacral cord Regulation of autonomic reflexes by higher centers interrupted Autonomic reflexes below the level of injury are uncontrolled, & above the level of injury remain under control of higher centers The higher the level of injury, the more are the effects;  Injuries T6 or above- problems regulating vasomotor tone  Below T6- adequate vasomotor tone Lower lumbar & sacral injuries- sympathetic function is not affected adu.edu Disruption of Autonomic Nervous System Function in SCI     Vasovagal response: visceral afferent input can cause vagal stimulation that causes a marked bradycardia, unchecked by a dysfunctional sympathetic NS Vasovagal response to endotracheal suction-can cause bradycardia, even asystole Postural hypotension: Injuries T6 or above- interruption of sympathetic tonic stimulation to BVs, VD & pooling of blood Impaired venous return & CO when in upright position adu.edu Disruption of Autonomic Nervous System Function in SCI        Autonomic Hyperreflexia: In injuries T6 & above Exaggerated sympathetic reflex responses, because of loss of CNS control of reflexes Stimuli initiating response may be a full bladder, rectum, pressure ulcers, painful stimuli Uncontrolled activation of local sympathetic reflexes below the level of injury VC below the level of injury- causes acute rise in BP Baroreceptors stimulated  Vagal slowing of HR  VD above the level of injury (flushed skin, headache) Is a clinical emergency adu.edu Porth’s pathophysiology