Neuro Flashcards
Frontotemporal dementia (Pick’s disease)
Atrophy of frontal and temporal lobes. Onset in 50’s and 60’s. Pick bodies: cytoplasmic inclusions of microtubule-associated protein tau. Apathy, socially inappropriate behavior. Autosomal dominant in 20%-40% of cases.
How do nondepolarizing NMJ blockers (e.g. vancuronium) present on train-of-four (TOF) stimulation?
TOF is used to assess the degree of NMJ block (a peripheral nerve is stimulated 4 times in quick succession and the response is recorded). Nondepolarizing NMJ blockers (e.g. pancuronium, vancuronium) cause a progressive reduction in the 4 responses (fading pattern).
How do depolarizing NMJ blockers (e.g. succinylcholine) present on train-of-four (TOF) stimulation?
TOF is used to assess the degree of NMJ block (a peripheral nerve is stimulated 4 times in quick succession and the response is recorded). Depolarizing blockers initially function by preventing repolarization of the motor endplate and show equal reduction in all 4 twitches (phase I blockade). Persistent exposure to succinylcholine will lead to a phase II blockage in which ACh receptors become desensitized and inactivated leading to a fading pattern on TOF.
What are the signs of uncal herniation?
Causes ipsilateral oculomotor nerve palsy with a fixed dilated pupil due to damage to the preganglionic parasympathetic fibers running on the outer portion of the 3rd cranial nerve.
How does a Chiari type I malformation present?
Usually presents during adolescence/adulthood with paroxysmal occipital headaches (due to meningeal irritation) and cerebellar dysfunction (e.g. dizziness and ataxia) due to compression of the cerebellar tonsils. It is due to underdevelopment of the posterior fossa, causing the cerebellar tonsils to extend down into the foramen magnum.
How do Chiari type II (Arnold-Chiari) malformations present?
More severe type of malformation - usually becomes evident in the neonatal period. Due to the underdevelopment of the posterior fossa, the cerebellum (vermis, tonsils) and medulla herniate through the foramen magnum. This leads to non-communicating hydrocephalus (usually due to aqueductal stenosis). Compression of the medulla may present as dysphagia, stridor and apnea. Patients often have an associated lumbar myelomeningocele, which may result in lower limb paralysis.
Which anti-epileptic is preferred for combination tonic-clonic and absence seizures?
Valproate
What is Ménière disease?
Caused by increased pressure and volume of endolymph. It causes recurrent vertigo, ear fullness/pain, and unilateral hearing loss and tinnitus.
Why is IV dopamine not able to reach the brain?
Because of tight junctions in the BBB composed of transmembrane proteins (e.g. claudins and occludins). L-DOPA (dopamine precursor) is able to cross, however, due to amino acid transporters at the blood-brain barrier.
What is akathisia?
Restlessness with inability to sit still
What area of the brain is damaged in Wilson’s disease?
Causes cystic degeneration of the putamen
During amniocentesis, which two markers are found to be elevated when a fetus has a neural tube defect?
Alpha-fetoprotein and acetylcholinesterase (both can leak out of the spinal canal into the amniotic cavity).
What is the treatment for neuroleptic malignant syndrome (NMS)?
Discontinuing the causative agent (e.g. antipsychotic) and give dantrolene (direct-acting msucle relaxant). Dantrolene can reduce muscle rigidity/contraction by antagonizing the ryanodine receptors, thereby inhibiting calcium ion release from the sarcoplasmic reticulum of skeletal muscle. Bromocriptine, a dopamine agonist, has also shown clinical benefit.
What are features of narcolepsy?
Charaterized by overwhelming urges to sleep. Commonly associated with cataplexy (sudden loss of muscle tone that occurs in response to intense [usually positive] emotions). Patients have shortened sleep latency and typically enter REM sleep almost immediately. There are often intrusions to REM sleep during sleep-wake transitions, including hypnagogic (upon falling asleep) and hypnopomic (upon awakening) hallucinations and sleep paralysis. Diagnosis can be confirmed by low CSF levels of hypocretin-1 or shortened REM sleep latency on polysomnography.
What is the consequence of damage to the subthalamic nucleus?
Contralateral hemiballism (a movement characterized by wild, involuntary, large-amplitude flinging movements involving the proximal limbs on one side of the body). This is due to loss of inhibition of the thalamus (the subthalamic nucleus decreases excitation of the globus pallidus internus, thereby reducing inhibition of the thalamus). Damage most commonly occurs in the setting of lacunar stroke as a consequence of long-standing HTN and diabetes.
What is chorea?
Involuntary, low-amplitude movements involving the distal limbs.
What does the neuroectoderm give rise to?
Central nervous system, preganglionic autonomic neurons, retina, and posterior pituitary.
What medications are effective for treating the spasticity associated with multiple sclerosis?
The spasticity associated with MS is due to loss of descending inhibitory control from the upper motor neurons resulting in lower motor neuron overactivity (increased tone and hyperreflexia). Baclofen, a GABA-B receptor agonist is effective monotherapy for treatment of spasticity. Tizanidine, an alpha-2 adrenergic agonist, is also effective and commonly used.
What is Werdnig-Hoffman syndrome?
It results from anterior cell horn cell damage. Lower motor neuron lesion signs are present (flaccid weakness, areflexia, muscle atrophy, and fasiculation - “floppy child” syndrome).
What is Eaton-Lambert syndrome?
It clinically resembles myasthenia gravis. It is a paraneoplastic syndrome associated with small cell lung carcinoma, and is explained by autoantibodies that react with presynaptic calcium channels and hamper release of ACh.
What effect do fluorinated anesthetics have on the vasculature of the CNS?
Decrease vascular resistance in the brain leading to increased cerebral blood flow. It is an undesirable effect as it results in increased intracranial pressure.
Other effects are: myocardial depression that decreases CO (causes hypotension), respiratory depression, decreased GFR, decreased renal plasma flow, and decreased hepatic blood flow.
What are lacunes?
Small cavitary infarcts (liquefactive necrosis) located within the basal ganglia, posterior limb of the internal capsule, pons, and cerebellum. They result from occlusion of small penetrating arteries that supply the deep brain structures (e.g. lenticulostriate arteries), most commonly in the setting of chronic uncontrolled HTN or DM. Lipohyalinosis (hyaline thickening of the vascular wall with foamy macrophages) and microatheromas (atherosclerosis within the intimal layer of a penetrating artery near its origin off the parental vessel) are believed to be the primary cause of lacunar infarcts.
What are the manifestations of Wernicke encephalopathy?
Ataxia, nystagmus, ophthalmoplegia, and anterograde amnesia. The chronic effects of thiamine deficiency lead to Korsakoff psychosis, which is characterized by anterograde and retrograde amnesia, apathy, lack of insight, and confabulation.
What is the drug entacapone?
An COMT inhibitor used to treat Parkinson’s. COMT peripherally methylates levodopa, limiting its half-life. Entacapone can be added to levodopa/carbidopa therapy in patients that experience end-of-dose “wearing off” periods because the drug produces more stable levodopa plasma concentrations.
What is Gerstmann syndrome?
A constellation of: agraphia (inability to write), acalculia (inability to carry out mathematical calculations), finger agnosia (inability to identify individual fingers on the hand), and left-right disorientation. It is due to damage to the angular gyrus of the dominant parietal lobe, a brain region supplied by the middle cerebral artery.
How is restless leg syndrome treated?
Dopamine agonists (e.g. ropinirole, pramipexole), avoidance of aggravating behaviors (e.g. alcohol, sleep deprivation), and supportive measures (e.g. leg massage, exercise, heating pads).
Iron deficiency is also common in RLS; low iron levels have been found in the substantia nigra of patients with RLS, even in the absence of systemic iron deficiency.
