CNS- II Flashcards
1
Q
What is ALS?
A
- Most common motor neuron diseases causing muscular atrophy
- death of upper motor neurons (betz cells- responsible to fast conduction) and degerneration of axons/lateral corticospinal tract
- death of lower motor neurons (located in anterior horn spinal cord/brainstem)
- reactive gliosis in areas of degeneration
- affected motor units lose innervation
- progressive degerneration of axons causes loss of myelin
- nearby motor nerves may sprout axons in attempt to maintain function, but eventually nonfunctional scar tissue replaces normal neuronal tissue
2
Q
What is cause of ALS?
A
- genetic (familial ALS “FALS”) link is seen in 10-20% of all ALS cases (defects in enzyme superoxide dismutase gene)
- over 90% of cases of ALS occur randomly with no identifiable cause and no risk factors and are referred to as sporadic ALS
- Histology: protein aggregates (TDP-43) within cytoplasm of motor neurons
- provides clues, but don’t know how to interpret increased dying)
3
Q
What are some current theories for causes of ALS?
A
- Glutamate excitotoxicity- excess glutamate causes Ca to go into cell (particularly NMDA) then extra Ca causes apoptosis in the cell
- oxidative injury
- protein aggregates
- autoimmune-induced calcium influx
- viral infections
- deficiency of nerve growth factor
- trauma
- environmental toxins
Current research suggests an excess of glutamatergic signaling in the synaptic cleft
4
Q
What is the prognosis of ALS?
A
- Chronic, progressively debilitating disease- death in as little as 1 year survivial up to 10 years
- men affected 3:1, average age 50 years
5
Q
ALS signs and symptoms?
A
- Fasciculations, spasticity, atrophy, weakness, and loss of funcitoning motor units (especially in forearms and hands)
- impaired speech, chewing, and swallowing; choking; drooling
- difficulty breathing, especially if brain stem affected
- muscle atrophy
- autonomic dysfunction- as brainstem more impacted, issues with hemodynamic instability
- depression
6
Q
ALS diagnosis
A
- electromyography- abnormalities of electrical activity in involved musles
- muscle biopsy: atrophic fibers interspersed between normal fibers
- CSF analysis by lumbar punction: elevated protein levels
7
Q
ALS treatment?
A
- Riluzole: glutamate antagonist and increases glutamate reuptake<– less glutamate in cleft. decreases preogression for a couple of months
- symptomatic
- baclofen or diazepam
- gabapentin, amitriptyline- for pain
- physical therapy
- percutaneous feeding tubes
- tacheostomy
8
Q
What are seizures?
A
- abnormal electrical discharges of neurons in the brain
- transient, paroxysmal and synchronized discharges of groups of neurons
- group of neurons firing inappropriately
9
Q
Causes of seizure disorders?
A
- Half of all cases are idiopathic
- birth trauma; anoxia; perinatal infection; genetic abnormalities, such as tuberous sclerosis and phenylketonuria; perinatal injuries
- metabolic abnormalities, such as hypoglycemia, pyridoxine deficiency (Vit B6) or hypoparathyroidism
- brain tumors or other space-occupying lesions
- meingitis, encephatlitis, brain abscess
- traumatic injury
- toxins: mercury, lead or carbon monoxide
- stroke
- familial incidence in some sz disoder
10
Q
Pathophysiology of seizures?
A
- epileptogenic focus: hyperexcitable neurons depolarize more readily when stimulated
- membrane potential at rest is less negative or inhibiotry connections are missing
- may be due to decreased GABA activity or localized shifts in electrolytes
- on stimulation, epileptogenic focus fires and spreads electrical current toward the synapse and surrounding cells
- if impulse cascades on one side of brain (partial seziure) OR
- impulse can go down both sides of brain (generalized seizure) or cortical, subcortical, or brain stem areas
- Brain’s metabolic demand for oxygen increases dramatically during a seizure
- can lead to hypoxia and neuronal cell death
-
firing of inhibitory neurons causes the excitatory neurons to slow their firing and eventually stop
- if this inhibitory action doesn’t occur, the result is status epilepticus
11
Q
What is status epilepticus?
A
one prolonged seizure or a series of seziures (>2) without regaining consciousness
- may be fatal (emergency)
- using up ATP, increase anaerobic metabolism, increase CO2, and other anaerobic metabolites… eventually can cause neuronal death
- rule out hypoglycemia
- metabolic acidosis & hyperthermia often ensue requiring controlled ventilation and cooling measures
- problematic because decreasing o2 available to brain
12
Q
What is a generalized tonic clonic sezure?
A
- altered consciousness
- tonic stiffening followed by clonic muscular contractions
- tongue biting
- incontinence
- labored breathing, apnea, cyanosis
13
Q
What is an absence seizure?
A
- change in level of awareness
- blank stare
- automatisms (purposeless motor activity)
14
Q
What are atonic seizures?
A
sudden loss of postural tone
temporary loss of alertness
15
Q
What are myoclonic seizures?
A
brief muscle contractions that appear as jerks or twitching
16
Q
What shows on EEG for seizure diagnosis?
A
- Tonic-clonic seizures, high, fast, voltage spieks are present in all leads
- absence seizures. rounded spike wave complexes are diagnostic
- a negative EEG doesn’t rule out epilepsy because the abnormalities occur intermittently
17
Q
What is treatment for seizures?
What are the big drug s/e?
What’s given for generalized tonic/clonic or complex partial seziures?
What’s given for absence seizures?
Surgeries to treat seizures?
A
- multiple drugs sometimes required for control
- drugs have many interactions and toxic effects
- examples: sedation (all), adverse hematologic reactions, rashes, developmental delay
- drug therapy speicfic to the type of seizure, including phenytoin, carbamazepine, phenobarb, for generalized tonic-clonic seizures and complex partial seizures
- VPA, clonazpam for absence seizures
- surgical removal of demonstrated focal lesion, if drug therapy is ineffective: temporal lobectomy
- may have residual hemiparesis
- surgery to remove the underlying cuase, such as tumor, abscess, or vascular problem
- vagal nerve stimulator implant: may have hoarsenss
- IV diazepam, lorazepam, phenytoin, or phenobarb for status epilepticus
- administration of dextrose (when seizures secondary to hypoglycemia) or thiamine (in chornic alcholism or withdrawal)
18
Q
What is normal CBF?
A
- Intact autoregulation= normal CBF 50 mL/100 g brain tissue per minute
- 1500 g brain with normal CO (5L/min)= CBF 750 mL/min
- 15% of cardiac output
- CBF is autoregulated
19
Q
What is normal CRMO?
A
- CRMO= 250 mL/min
- 18-23% of total body oxygen consumption
- CMRO can be decreased by temp reducitons and various anesthetic agents
- CMRO increased by temperature increases and seizures
20
Q
How much does CBF increase for every 1 mmHg increase in PaCO2?
A
CBF increase by 1-2 mL/100g/min for every 1 mmHg increase in PaCO2
- Decrease occurs during hypocarbia, so that CBF is decreased by approximately 50% when PaCO2 is acutely reduced to 20 mmHg
- 6 hours: return of CSF pH to normal; hypocarbia no longer able ot significantly reduce CBF
21
Q
What happens when Pao2 is <50 mmHg?
A
- Cerebral vasodilation and increased CBF
- “hail mary”
22
Q
What is normal ICP? What is it determined by? When can it increase?
A
- Normal 5-15 mmHg
- Determined by
- rigid cranial vault fixed volume (total 1200-1500 mL)
- brain (cellular and ICF) (80%)
- `hyperosmotic diuretic to get rid fo fluid
- blood (arterial and venous) (12%)
- if compressing jugular vein, increase vneous back up into head and increase venous blood volume
- never want blood vessels dilated because increase volume
- CSF (8%)
- brain (cellular and ICF) (80%)
- rigid cranial vault fixed volume (total 1200-1500 mL)
- Increase ICP with intracranial bleeding, hydrocephalus, tumor, edema, following traumatic injury, etc
- with brian injury, increase blood and increase brain edema problematic
- if brain expands, compresses agaisnt bone/dura mater
23
Q
What is CPP?
A
- Cerebral perfusion pressure= MAP- ICP (or cvp, whichever is greater)
- Normal is 80-100 mmHg
- CPP < than 50 mmHg- slowing seen on EEG
- CPP between 25-40 flat EEG
- CPP <25 mmHg sustained = irreversible brain damage
- variables affecting CBF during anesthesia: PaO2 AND PaCO2, systemic blood pressure, ICP, cerebral autoregulation and various drugs
24
Q
Management of increased ICP?
A
Maintain CPP and cerebral blood flow (decrease ICP <20 mmhg and increase BP)
- Mannitol (0.25-0.5 g/kg)/hypertonic saline 1-2 mL/kg over 5 minutes
- furosemide
- vasopressors- if increased ICP, then you need to maintain arterial BP high enough to ensure blood flow to brain! (think CPP= MAP-ICP!)
- PaCO2= low normal 30-35 mmHg (6 hours)
- maintain normothermia
- barbiturate/propofol coma- get EEG down to almost flat to bring O2 demand down. Allows all O2 in brain to go towards housekeeping/normal integrity
- CSF drainage if available (ventriculostomy)
- HOB 30 degrees- encourage venous outflow
- Corticosteroids (only in brain tumor patients)
- Surgical decompression and/or craniecromt (TRAUMA)
25
Q
What is herniation?
A
- extreme result of increased ICP
- Various types of herniation syndromes are categorizes based on region of brain affected
- severe ICP elevation leads to decreased levels of consciousness and coma
- acute increases in ICP may not be tolerated as well as chronic intracranial HTN
26
Q
What happens with subfalcine herniation?
A
- primary motor cortex compression of anterior cerebral artery
- aka- herniation of cingulate gyrus under the falx cerebri
27
Q
What happens with transtentorial herniation?
A
- this is a herniation of contents over the tentorium cerebelli
- causes posterior cerebral artery compression
- can see pupillary dilation on affected side and loss of reflexes
- issue with vision
