Goljy 26: Nervous System and Special Sensory Disorders Flashcards
intracellular edema
water moves into cells
caused by:
1. dysfunctional Na+/K+-ATPase pump
2. Hyponatremia causing osmotic shift
extracellular edema
d/t increased vessel permeability
caused by:
1. acute inflammation
2. metastasis, trauma, lead poisoning
Why is a person with head trauma purposely hyperventilated?
- to produce respiratory alkalosis –> cerebral vessel constriction
- decreases risk of increased vessel permeability and edema
What effect do respiratory acidosis and hypoxemia have on cerebral vessels?
- vasodilation –> increased vessel permeability –> edema
Signs of increased intracranial pressure
- papilledema
- headache, projectile vomiting w/o nausea
- sinus bradycardia, hypertension
- potential for herniation
pseudotumor cerebri
- increased intracranial pressure without evidence of tumor/obstruction d/t decreased CSF resorption in arachnoid villi (equilibration in inflow/outflow eventually occurs)
- papilledema is present, no mental status change/focal neurologic signs
- MC young obese women, other risks: ATRA used for APML, hypothyroid, Cushing disease, BC pills, isotretinoin, tamoxifen
pseudotumor cerebri Sx, Dx, Tx
Sx: headache, rhythmic sound in one/both ears, diplopia, blurry vision
Dx: MRI - flattening of posterior globe
CSF pressure increased, decreased CSF protein
Tx: carbonic anhydrase inhibitor or systemic corticosteroids if visual disturbances present, lumboperitoneal shunt, optic nerve sheath fenestration
cerebral herniation
a complication of intracranial hypertension where portions of the skull become displaced through either openings in the dural partitions or openings of the skull
subfalcine herniation
- cingulate gyrus herniates under the falx cerebri
- herniation causes compression of the anterior cerebral artery
uncal herniation
- medial portion of the temporal lobe herniates through the tentorium cerebelli
- Can cause:
1. Compression of the midbrain –> Duret hemorrhage
2. Compression of CN III –> eye deviates down and out, pupil is dilated d/t compression of parasympathetic postganglionic fibers
3. compression of posterior cerebral artery –> hemorrhagic infarction of occipital lobe
tonsillar herniation
- cerebellar tonsils herniate into foramen magnum
- “coning” of cerebellar tonsils
- cardiorespiratory arrest
hydrocephalus
increase in CSF volume –> enlargement of ventricles
production and movement of CSF
- produced by choroid plexus in ventricles
- exists fourth ventricle thru foramina of Luschka and Magendia and enters subarachnoid space
- reabsorbed by arachnoid villus into dural venous sinuses
Communicating hydrocephalus
- open communication btwn ventricles and subarachnoid space
- Causes:
1. increased CSF production
2. obstruction in reabsorption of CSF by arachnoid villi
Noncommunicating hydrocephalus
- obstruction of CSF flow out of ventricles
- Causes:
1. stricture of aqueduct of Sylvius - MCC in newborns –>paralysis of upward gaze
- pineal gland tumor
2. Tumor in fourth ventricle
3. scarring at base of brain
4. colloid cyst in 3rd ventricle
5. various developmental disorders
Clinical findings in hydrocephalus
Newborns: ventricles dilate and enlarge head circumference
Adults: ventricles enlarge but NO increase in head circumference
hydrocephalus ex vacuo
- dilated appearance of the ventricles when the brain mass is decreased from cerebral atrophy, eg. Alzheimer’s
Normal pressure hydrocephalus
Dilated ventricles and “wet wide and wacky” sx:
- urinary incontinence
- wide based gait
- dementia
Causes:
idiopathic
secondary to subarachnoid hemorrhage, intracranial surgery, trauma
Pathogenesis of normal pressure hydrocephalus
- subarachnoid space volume is increased
- ventricular dilation is out of proportion to sulcal atrophy
- wide based gait and urinary incontinence d/t stretching of sacral nerve fibers near dilated ventricle
- dementia d/t stretching of limbic fibers near dilated ventricle
normal pressure hydrocephalus dx and tx
Dx: MRI shows ventriculomegaly, sulcal atrophy
Large volume of CSF is removed at lumbar puncture, symptoms improve w/ removal of fluid
Tx: ventriculoperitoneal or ventriculoatrial shunt
Neural tube defect
- Failure of the fusion of the lateral folds of the neural plate
- Rupture of a previously closed neural tube
- Maternal folic acid levels must be adequate BEFORE pregnancy to prevent open neural tube defects
Maternal findings in neural tube defect
Increased maternal AFP in serum and/or amniotic fluid in anancephaly, meningocele, or myelomeningocele but NOT spina bifida occulta
Anancephaly
- complete absence of the brain
- frog-like appearance
- open spinal canal
- maternal polyhydramnios
Spina bifida occulta
- defect in closure of the posterior vertebral arch
- dimple or tuft of hair in the skin overlying L5-S1
meningocele
- spina bifida with cystic mass containing meninges
- MC in lumbosacral region
meningomyelocele
- spina bifida with cystic mass containing meninges and spinal cord
- MC in lumbosacral region
Arnold-Chiara malformation
- caudal extension of the medulla and cerebellar vermis through foramen magnum
- noncommunicating hydrocephalus
- platybasia
- a/w meningomyelocele, syringomyelia
- Tx: decrompression surgery
Dandy-Walker malformation
- partial or complete absence of the cerebellar vermis
- cystic dilation of the fourth ventricle
- noncommunicating hydrocephalus
- Tx: shunt to treat hydrocephalus
syringomyelia
- degenerative disease of the spinal cord
- Sx usually appear in 3rd of 4rd decade
- fluid-filled cavity (syrinx) within cervical spinal cord
- produces cervical cord enlargement
- cavity expands and causes degeneration of spinal tracts
Pathogenesis of syringomyelia
- obstruction of outflow from fourth ventricle
- birth injury
Clinical findings in syringomyelia
- disruption of the crossed lateral spinothalamic tracts –> pain and temp lost in the hands, tactile sense preserved
- destruction of anterior horn cells –> atrophy of intrinsic muscle of the hands, often confused with ALS
- Charcot joint in shoulder, elbow, or wrist
Dx and Tx of syringomyelia
Dx: MRI shows enlarged cervical cord and a cystic cavity
Tx: drainage of syrinx slows progression
Phakomatoses
- neurocutaneous syndromes including:
1. disordered growth of ectodermal tissue
2. malformationf or tumors of the CNS
Neurofibromatosis
AD w/ incomplete penetrance, no gender predominance
- Type 1: MC, mutation on chromosome 17 coding for neurofibromin
- Type 2: mutation on chromosome 22 coding for merlin
NF1
- cafe au lait spots
- optic gliomas
- Lisch nodules
- axillary and inguinal freckling
- mild scoliosis
- pigmented plexiform neurofibromas
- pigmented cutaneous/subcutaneous neurofibromas
a/w: pheochromocytoma, Wilms tumor, juvenile CML
NF2
a/w bilateral acoustic neuromas (CN8 benign tumor –> hearing loss, tinnitis), meningiomas, spinal schwannomas, juvenile cataracts
Tuberous sclerosis
AD, mental retardation and seizures beginning in infancy
- angiofibromas on the face
- hypopigmented skin lesions called shagreen patches/ash leaf spots
- subungal or periungal fibromas
- hamartomas: astrocyte proliferations, angiomyolipomas in kidneys, rhabdomyoma in the heart
Sturge- Weber syndrome
- somatic mosacism or sporadic
- vascular malformation on the face in trigem nerve distribution
- some patients have ipsilateral AV malformation in meninges
cerebral contusion
permanent damage to small blood vessels and the surface of the brain, most often secondary to an acceleration-deceleration injury
Coup injury
occurs at site of impact
Contrcoup injury
occurs opposite the site of impact, MC tips of frontal and temporal lobes
epidural hematoma
- arterial bleed creates a blood-filled space between the bone and dura
- caused by a fracture of the temporoparietal bone –> severance of the middle meningeal artery
- increased ICP –> herniation and death
- Dx: CT
- hematoma rarely crosses suture line
- Tx: burr holes to relieve pressure
subdural hematoma
- venous bleeding between the dura and arachnoid membranes
- MC d/t blunt trauma, also: medical anticoagulation, hemophilia, child abuse, spontaneous
- Risk factors: old people and alcoholics with brain atrophy
- tear in bridging veins between brain and dural sinuses are torn, causes venous blood clot
- herniation and death, chronic: dementia
- Tx: burr holes to relieve pressure
3 categories of cerebrovasular diseases:
- thrombosis
- infarction
- hemorrhage
Causes of cerebrovascular disease:
- Reduced blood supply and O2 of tissue
- CNS hemorrhage from rupture of cerebral vessels
Global hypoxic injury
Causes: cardiac arrest, hypovolemic shock, septic shock, CO poisoning
Complications: cerebral atrophy (necrosis of neurons in layers 3, 5, 6 of cerebral cortex), Watershed infarcts at the junctions of arterial territories, stroke
Stroke
sudden loss of blood circulation to an area of the brain resulting in a loss of neurologic function
- risk increases w/ age
Atherosclerotic stroke
MC type of stroke
- ischemic type of stroke caused by a platelet thrombosis that develops over a disrupted atherosclerotic plaque
- Common locations: MCA, internal carotid artery near bifurfaction, basilar artery
- Prevention: aspirin, clopidogrel
Gross/microscopic findings in atherosclerotic stroke
- Develops at the periphery of the cerebral cortex –> pale infarct
- Swelling of the brain, loss of demarcation btwn grey and white matter, myelin breakdown
- Gliosis
- Cystic area develops after 10 days-3 weeks d/t liquefactive necrosis
Transient ischemic attack
Transient episode of neurologic dysfunction caused by focal brain/spinal cord/retinal ischemia without infarction
amaurosis fugax
a retinal TIA caused by microembolization of atherosclerotic material to a bifurcation of the retinal arteries
Tx of TIA
- Antithrombic therapy
- Antiplately therapy
- possible carotid endarectomy/stenting
Strokes involving MCA
- contralateral hemiparesis and sensory loss in the face and upper extremity
- expressive aphasia if Broca’s area is involved in L hemisphere
- visual field defects
- head and eyes deviate toward site of lesion
Strokes involving ACA
Contralateral hemiparesis and sensory loss in lower extremity
Strokes involving vertebrobasilar arterial system
- vertigo, ataxia
- ipsilateral sensory loss in the face
- contralateral hemiparesis and sensory loss in trunk and limbs
Embolic stroke
- Ischemic type of stroke due to embolization
- Emboli MC originate from L side of heart
- produces a hemorrhagic infarction (MC in MCA, reperfusion after lysis of embolic material –> hemorrhage)
Sources of emboli
- Mural thrombi in LV after AMI, aortic/mitral valve vegetations, L. atrium in a fib
- A fib d/t thrombus formation in LA from stasis of blood
- “Shower” embolization (emboli blocking numerous small vessels)
Intracerebral hemorrhage
Most often d/t stress imposed on vessels by hypertension
- branches of lenticulostriate vessels develop Charcot-Bouchard microaneurysms
- rupture of aneurysms –> intracerebral hemorrhage
Common sites of intracerebral hemorrahage
Basal ganglia, thalamus, pons and cerebellar hemispheres
Slit hemorrhage
A/w hypertension
Rupture of small caliber penetrating vessels, producing hemorrhages that resorb blood, leaving slit-like spaces with a brownish-red pigment
Subarachnoid hemorrhage
- Majority secondary to rupture of berry aneurysm
- Can also be d/t bleeding from an AV malformation
Berry aneurysm
yum yum berries
Risk factors: normal hemodynamic stress, hypertension, coarctation of aorta, atherosclerosis, smoking
Most develop at junctions of communicating branches with main cerebral artery - junctions lack internal elastic lamina and smooth muscle
MC site is junction of the anterior communicating branch with ACA
Rupture releases blood into subarachnoid space
Blood in CSF is broken down into bilirubin pigment –> xanthochromia
Clinical findings in subarachnoid hemorrhage
“Worst headache ever”
Nuchal rigidity from blood irritating meninges
50% mortality
Complications: further hemorrhage, hydrocephalus, neurologic defects
Lacunar infarct
- Cystic area of microinfarction
Dx of stroke
CT scan without contrast, distinguishes hemorrhage from nonhemorrhagic stroke
Tx of stroke
Acute: Thrombolytic therapy in thromboembolic strokes (
Pathogenesis of CNS infections
- Hematogenous (MC)
- Traumatic implantation
- Local extension from nearby infection
- Ascent via peripheral nerve
Meningitis
- Inflammation of pia mater covering the brain
- Usually d/t hematogenous spread
Pathogenesis of bacterial meningitis
Adherence of bacteria to mucosa of nasopharynx >
Bacteremia >
Translocation through the BBB using bacterial lysins >
Bacterial in the subarachnoid space attract neutrophils >
Acute meningitis
Risk factors for bacterial meningitis in kids
- undernutrition, otitis media
- pneumonia, immunodeficiency
- viral infection, sickle cell
- craniofacial abnormality
Viral meningitis
Mostly fecal-oral, respiratory less common
Clinical findings and complications of meningitis
Clinical: Fever, nuchal rigidity, headache
Complications: Seizures, focal neurolog deficits, cranial nerve palsies, sensorineural hearing loss, communicating and noncommunicating hydrocephalus
Lab findings in viral meningitis
- Increased CSF protein
- Increased total CSF leukocyte count (lymphocytes)
- Normal CSF glucose
Lab findings in bacterial meningitis
- Increased CSF protein
- Increased total CSF leukocyte count (neutrophils)
- Decreased CSF glucose
Lab findings in fungal meningitis
- Increased CSF protein
- Increased total CSF leukocyte count (lymphocytes)
- Decreased CSF glucose
Encephalitis
- Inflammation of the brain
- Fever, headache, impaired mental status, drowsiness
- Meningoencephalitis
Cerebral abscess
- Either spreads from an adjacent focus of infection OR hematogenous spread
- Single or multiple lesions
Demyelinating disorders pathogenesis
- Destruction of normal myelin
- Production of abnormal myelin
- Destruction of oligodendrocytes
Multiple sclerosis
- MC demyelinating disease, MC in females 20-40
- An autoimmune disease with genetic (HLA-DR2) and environmental (microbial pathogens, vitamin D, sun exposure) factors
Pathogenesis of MS
- CD4+ TH1 cells and TH17 cells react against self myelin antigens (type IV hypersensitivity)
- CD4+ TH1 cells secrete IFN-gamma–> activates macrophages, TH17 releases cytokines to recruit neutrophils + monocytes
- Leukocytes + TNFa attack myelin sheath and oligodendrocytes –> demyelination
- Antibodies produced by autoreactive B cells are directed towards myelin sheath and oligodendrocytes as well (type II hypersensitivity)