General Flashcards
Long-term use of proton pump inhibitors to decrease gastric acid production is associated with which of the following serum deficiencies?
B12 (Cyanocobalamin)
How does PTH therapy work in patients with osteoporosis?
Activation of osteoblasts function via PTH/PTHrP type 1 receptors
Parkinsonism is seen most commonly following toxic exposure to which of the following agents?
manganese
can also be produced by carbon disulfide, carbon monoxide, cyanide, MPTP, and organic solvents
antiemetics including metoclopramide and prochlorperazine have significant antidopaminergic activity and can cause drug-induced Parkinsonism.
What type of drug is Phenoxybenzamine?
Phenoxybenzamine is an alpha-adrenergic blocker. Propranolol is a beta-adrenergic blocker. Clonidine is an alpha agonist. Albuterol is a beta agonist. Dobutamine is a beta and alpha agonist
The medication most commonly used for management of Ménière disease is an antagonist of which of the following receptor types?
One of the most common drugs used to treat Menieres disease is betahistine which is an antagonist of histamine H3 receptors.
The other main class of drugs used to treat Menieres disease are diuretics. The most common diuretics used to treat Menieres disease are thiazides with or without potassium-sparing diuretics such as hydrochlorothiazide/triamterene or spironolactone as well as the carbonic anhydrase inhibitor acetazolamide as a second-line therapy.
intravenous tissue plasminogen activator (tPA) be administered no later than how long after the onset of acute ischemic stroke?
Initial studies demonstrated benefit for intravenous tPA given 0-3 hours after stroke onset. A later publication demonstrated utility of tPA up to 4.5 hours after stroke onset.
Numerous mechanical thrombectomy trials for patients with large vessel occlusion acute ischemic strokes have demonstrated efficacy in both “early” and “late” windows, expanding the indication for this intervention to 24 hours.
Which of the following is the correct spinal cord location for percutaneous cervical cordotomy on a patient with unilateral cancer pain?
Percutaneous cordotomy targets the contralateral spinothalamic tract in patients with unilateral somatic pain, primarily cancer related pain.
First order spinal nerve axons enter the ipsilateral dorsal root, before they terminate in the dorsal horn. Second order axons then travel across the anterior white commissure and ascend via the spinothalamic tract, where they are arranged somatotopically.
This is an excellent procedure for the treatment of cancer pain located at or below the C5 dermatomal level for patients with limited life expectancy.
A patient who takes vitamin supplements reports headaches, diplopia, and diffuse myalgias. Examination shows papilledema and dry, scaly skin. The patient is most likely consuming an excess of which vitamin?
The clinical scenario best describes a patient with chronic vitamin A toxicity.
Vitamin C toxicity can lead to GI symptoms, fatigue, and nephrolithiasis due to increased calcium oxalate formation.
Vitamin E toxicity is rare but can cause increased risk of bleeding and coagulopathy as high doses may alter Vitamin K metabolism.
Niacin and Pyridoxine are B vitamins which can be associated with facial flushing and sensory peripheral neuropathy when taken in excess, respectively.
Inheritance pattern of Duchenne’s muscular dystrophy and myotonic distrophy?
Duchenne’s muscular dystrophy is transmitted in an X-linked fashion. Myotonic dystrophy is transmitted in an autosomal dominant fashion.
What characteristic imaging finding on MRI would best differentiate neuromyelitis optica from multiple sclerosis?
A longitudinally-extensive spinal cord lesion is most consistent with neuromyelitis optica (NMO) and is helpful in differentiating it from multiple sclerosis. NMO, or Devic disease, once thought to be a form of multiple sclerosis, is associated with bilateral optic neuritis, longitudinally-extensive transverse myelitis, and antibodies to the aquaporin 4 water channel.
Diagnosis of NMO require optic neuritis, myelitis, and two of the following: a longitudinally extensive spinal cord lesion on MRI (extending 3 or more segments), brain MRI not initially meeting criteria for MS, or NMO-IgG seropositivity
Which T-scores defines osteoporosis?
T-score is defined as a standard deviation measurement resulting from a bone density test.
The World Health Organization (WHO) defines osteoporosis as having a T-score lower than -2.5. Osteopenia is defined as a T-score between -1 and -2.5.
Definition and drugs associated with causing RCVS:
Reversible cerebral vasoconstrictive syndrome (RCVS) is a clinical syndrome characterized by acute thunderclap headache, emesis and nausea
due to a transient disturbance in the control of cerebrovascular tone
segmental vasoconstriction on angiography and reversibility of the lesion
triggered by vasoactive substances, including SSRI such as sertraline, or cocaine
occur post partum or after exposure to adrenergic or serotonergic drugs.
uniphasic course, and vary from pure cephalalgic forms to rare catastrophic forms associated with hemorrhagic and ischemic strokes, brain edema, and death.
nimodipine seems to reduce thunderclap headaches within 48 hr of administration, but has no proven effect on hemorrhagic and ischemic complications.
Kearns-Sayre syndrome: inheritance, lab abnormalities, and symptoms?
AD
Ptosis, pigmentary retinopathy, ophthalmoplegia that can progress to deafness and CM
affected enzyme is mitochondrial DNA non maternally inherited
Increased serum pyruvate, spongy brain
progressive external ophthalmoplegia, retinitis pigmentosa, and cardiac conduction defects
refsums disease: inheritance, lab abnormalities, and symptoms?
AR
affected enzyme is phytanic acid oxidase
symmetric lower extremity peripheral neuropathy, retinitis pigmentosa, hearing loss, cardiomyopathy
hurler disease: inheritance, deficiency, lab tests, and symptoms?
AR alpha-L-iduronidase
increased urine dermatan, zebra bodies
MR, gargoyl face, thick meninges, spinal cord compression, corneal opacities, conduction deafness, cardiac disease
Behcets disease: vessel involved, pathology, clincal picture, treatment
small vessels (venules)
arterial occulsion, aneurysm, thrombophlebitis
mostly in males and present with: meningo-encephalitis, brain stem edema, confusion, oro-gential ulcers, uveitis, ulerative colitis, erythema nodosum, polyarthritis
tx: steroids
What is tetrodotoxin?
voltage gated sodium channel blocker
what is tetraethylammonium (TEA)?
voltage gated K channel is inhibitor
what is the conduction velocity in large, myelinated fibers?
as high as 120m/s
Where is ACh found? what inhibits acetylcholinesterase?
nucleus basalis of meynert, motor cortex, skeletal muscle, preganglionic autonomic nerves (N), postganglionic parasympathetic nerves (M), and postganglionic sympathetic nerves supplying sweat glands (M)
M= muscarinic, G protein coupled receptors, blocked by pertussis toxin, atropine, scopalamine. Stimulated by bethanacol, carbacole, pilocarbine
all others are nicotinic, blocked by hexamethonium, succinocholine, tubocurare
AChE inhibited by neostigmine, physostigmine, endophronium…
Where are dopamine and NE found? What is the tyrosine to dopamine/NE pathway? What is the rate limiting step?
NE: pontine locus ceruleus and postganglionic sympathetic nerve fibers
dopamine: substansia nigra, ventral tegmental area, and arcuate nucleus of hypothalamus
both breakdown to VMA and HMA, respectively
In pathway, tyrosine hydroxylase is the rate limiting step
dopamine cannot cross BBB, only L-dopa
NE is synthesized in vesicles
Which are the inhibitory neurotransmitters? Where are they found?
dopamine
glycine (found in the spinal cord; renshaw cells)
GABA: found in the cortex, basal ganglia, cerebellum (purkinje cells) and spinal cord
serotonin-found in brainstem nuclei (median raphe nuclei) that project to the hypothalamus and spinal cord (dorsal horns). It acts to inhibit pain pathways, induces sleep, and affects mood. used by pineal gland to produce melatonin
Pathway of the spinothalamic tract:
carries sensory information through delta type A fibers (to thalamus for pain) and C fibers (slow pain fibers to reticular formation and periaqueductal grey.
sensory fiber ascends lissaurs tract and synapses on laminae 1,4,5 and 6
Fibers ascend in the anterior (i.e., ipsilateral) and lateral (i.e., contralateral, due to crossing of fibers in the anterior commissure, within three levels) spinothalamic tracts to the ventroposterolateral (VPL; body), ventroposteromedial (VPM; face), and posterior thalamic nuclei for touch and temperature sensations; then synapse in the somatosensory cortex
Fibers also relay impulses in the spinoreticular tract to the intralaminar thalamic nucleus for pain.
Can also synapse in the reticular formation, tectum, and periaqueductal gray for pain throuch c fibers
TLDR: spinothalamic tract –> medial/trigeminal lemniscus –> VPL.VPM/posterior thalamus –> S1
Six layers of neurons in the sensory cortex:
Layers 1 (most superficial; molecular layer) and 2 (association fibers; external granular layer) receive diffuse, nonspecific input from the lower brain and may control the excitability of a region.
Layers 3 (cortico-cortical association that connect one temporal lobe to the other and commissural fibers; external pyramidal layer/pyramidal cells) relay axons to other cortical areas
Layer 4 (internal granular layer) of each column does not interact with the other columns, whereas other layers do. Afferent fibers arrive in layer 4 and either spread up or down a column. Receives thalamocortical input and is enlarged in SENSORY cortices. forms external band of baillarger and white line of gennari
Layers 5 (internal pyramidal layer) and 6 (projection fibers; fusiform layer) disperse axons to distant parts of the nervous system. Layer 5 is larger and connects to the brainstem, basal ganglia, and spinal cord and is enlarged in MOTOR cortices, whereas layer 6 is smaller and connects to the thalamus.
Pyramidal cells are chief cortical efferents; stellate or granule cells are the main interneurons and are much more numerous.
pathway of the posterior column to the cortex:
Axons enter the spinal cord and divide into a medial branch that travels up the dorsal column (25% of fibers), and a lateral branch (75% of fibers) with multiple synapses in the dorsal horn for reflexes
Second-order neurons are located in the medulla, within the medially situated nuclei gracilis and laterally situated nuclei cuneatus
Arcuate fibers cross to form the medial lemniscus (ML), joining fibers from the main sensory nucleus of the trigeminal nerve (V) and the upper spinal nucleus of V to terminate in the thalamic VPL (body) and VPM (face).
The ventrobasal complex (VPL, VPM, and the posterior thalamic nucleus) sends fibers to the cortical somatosensory areas S1 and S2. A somatotopic organization exists with the lower limbs represented medially in the spinal cord, laterally in the thalamus, and medially again in the cortex
How do we sense proprioception (receptors) and what is the pathway?
The muscle spindles, Pacinian corpuscles, Ruffini’s end organs, and Golgi’s tendon organs of the extremities
Lower limb proprioception is conveyed within the lateral column from Clarke’s column neurons (rexed lamina 7) through the ipsilateral dorsal spinocerebellar tract to the cerebellum (through inferior cerebellar peduncle)(i.e., not in the posterior columns)
Upper extremity proprioception is conveyed through the posterior columns in the fasciculus cuneatus prior to synapsing onto the accessory cuneate nucleus in the caudal medulla, before being relayed to the cerebellum via the cuneocerebellar tract
Somatic association areas (Brodmann’s areas 5, 7):
located behind S1 and above S2
Receives input from S1, ventrobasal thalamus (VPL, VPM, posterior thalamic nucleus), visual cortex, and auditory cortex
Stimulation elicits complex body sensations
A lesion in this region results in amorphosynthesis (i.e., the inability to recognize or detect objects sensed contralaterally) and astereognosia
contributes to 2-point discrimination (1 mm in the finger, 30–70 mm in the back)
Pain pathway mediators are:
bradykinin, 5-hydroxytryptamine (5-HT; serotonin), histamine, K+, acids, acetylcholine (Ach), and proteolytic enzymes all activate pain receptors. Prostaglandins enhance pain receptor sensitivity, but do not themselves excite these receptors
Thalamic pain (Dejerine–Roussy) syndrome
usually due to a posteroventral thalamic stroke causing ataxia and contralateral hemianesthesia, which in subsequent weeks to months is characterized by not only a return of crude sensation but also increased pain and affective, unpleasant feelings. It may be caused by facilitation of the medial thalamic nucleus with increased transmission of reticular formation pain.
What structures are involved in memory?
dorsomedial thalamus, hippocampus, temporal cortex, ascending reticular activating system (ARAS), and neocortex
What is the memory pathway from the hippocampus?
hippocampus → precommissural fornix → septal gray → diagonal band of Broca → the amygdala
Characteristic pathologic findings for alzheimers disease are the following:
Neuronal loss and atrophy associated with generalized cortical atrophy—more pronounced in temporal and parietal lobes.
Neurofibrillary tangles—intraneuronal inclusion: Paired helical filaments formed by hyperphosphorylation of microtubule-associated protein tau.
Senile plaques: extracellular:
- Comprised of amyloid β peptides, proteolytic product of amyloid precursor protein (APP) located on chromosome 21;
- Average 50 μm in size;
- Overexpression is seen in Down’s syndrome and has symptoms of this disease by age 40 years;
- ApoE4 mutation leads to excessive accumulation of amyloid.
Hirano’s bodies: eosinophilic intracellular aggregates of actin and associated proteins in neurons.
histology of picks disease?
Pick’s bodies (intracellular inclusions of tau protein) and Pick’s cells (swollen neurons) are specific.
symptoms of wernicke’s encephalopathy?
ataxia and nystagmus.
Korsakoff’s psychosis with anterograde and retrograde amnesia and confabulation
pathology of lewy body dementia:
Typified by α-synuclein cytoplasmic inclusions referred to as Lewy’s bodies.
Loss of both ACh- and dopamine-producing neurons
symptoms of bilateral frontal lesions:
impaired gait and incontinence (lack of warning), pseudobulbar palsy (degeneration of corticobulbar pathways to cranial nerve [CN] V, VII, X, XI, and XII nuclei with sparing of III, IV, and VI).
A lesion in the supplemental motor cortex produces:
involuntary grasping (it normally inhibits this reflexive activity)
A lesion in area 6 (premotor area, anterior to motor cortex area 4) produces and what are the sensory inputs to area 6?:
spasticity by increased stretch reflexes.
Inputs are VL and SMA
A lesion in area 4 produces:
hypotonia and weakness of the contralateral distal limb, but no spasticity.
Uncinate fasciculus connects the:
anterior temporal lobe to the orbitofrontal gyrus
Arcuate fasciculus connects:
Wernicke’s to Broca’s area
Anterior commissure and middle corpus callosum connect the:
two temporal lobes
Definition: Kluver–Bucy syndrome—from bilateral amygdala injury.
Absence of emotional response, compulsion to explore all objects visually, tactilely, and orally; hypersexuality and visual agnosia.
Pleasure concentrated in which nucleus?
nucleus accumbens and septal nuclei
Stimulation of the globus pallidus (GP) can produce:
an experience of joy
Guilt, anxiety, and paranoia may be associated with the:
orbitofrontal cortex
What is the role and connections in the amygdala?
plays a role in emotion and fear; interconnected with olfactory system (afferent) and hypothalamus (efferent)
What causes pathological laughing or crying? What paths control movement?
injury to bilateral corticobulbar tracts from stroke, MS, or ALS
Three paths control the pontomedullary facial movements involved with laughing and crying:
The voluntary pathway involves the corticobulbar tract in the genu of the internal capsule (posterior).
The involuntary pathway is anterior to the genu of the internal capsule.
Damage to the anterior path causes unilateral decreased movement with emotion. Damage to the posterior path causes unilateral increased movement with emotion.
Erections and orgasms can be produced by stimulation of:
thalamic medial dorsal nucleus, medial forebrain bundle, and septal nuclei
Definition: stria medullaris
connects septal area, hypothalamus, olfactory area, and anterior thalamus –> habenula
Definition: Medial forebrain bundle
Connects septal area, hypothalamus, basal olfactory areas, hippocampus/subiculum → midbrain, pons, and medulla
Definition: Diagonal band of broca
connects septal nuclei –> amygdala
Definition: lamina terminalis
closed rostral end of the neural tube (formed by anterior neuropore that closes at embryonic day 24)
Definition: Golgi’s tendon organs—
encapsulated receptors with bundles of tendon fibers passing through them, located at the muscle–tendon junction
detects the tension within 10 to 15 contained muscle fibers.
afferent signal is mediated from type Ib fibers to interneurons that decrease α motor neuron output. The reflex is not monosynaptic. It prevents muscle tearing and serves to equalize forces in the muscle, such that tense fibers are allowed to relax.
Defintion: Myotatic (muscle stretch) reflex—
When a muscle is stretched, impulses travel from the spindle’s type Ia fibers to the α motor neuron; this induces contraction via a monosynaptic reflex. A damping mechanism smooths contractions from multiple sources to produce fluid (i.e., not jerky) movement.
area 6: consists of…, location, input, projections
premotor cortex (lateral) and SMA (medial)
input from VL and SMA to PMC
input from VL, area 4, and S1 to SMA
Majority of projections are to 4, 5, 7, and premotor cortex with subcortical efferents to thalamus (VL, VA, MD)
Taste pathway: cranial nerves, nuclei, innervation
CN 7, 9, 10 –> nucleus of the solitary tract –> VPM thalamus –> gustatory cortex in area 43
Motor thalamic nuclei: Projections and input
VA: input GPi and SNr. projects to frontal eye fields: area 8, PMC, SMA
VL: input SNr, GPi, and deep cerebellar nuclei. projects to SMA and primary motor cortex
aka as Voa
motor nuclei are found anterior to sensory. Important when targeting thalamus for DBS
Pallidothalamic fibers: pathway
consists of ansa lenticularis and lenticular fasciculus
projects to VA, VL, and IL (aka Voa)
what is the cerebellar output and input? What is the dentorubrothalamic tract?
input (afferents) mostly from inferior (restiform and juxtarestiform bodies; juxtarestiform carries primary and secondary vestibulocerebellar fibers) and middle peduncles
output through superior peduncle via dentorubrothalamic tract
purkinje cells –> dentate nucleus –> superior cerebellar peduncle (site of decussation) –> some to contralateral red nucleus and others to VL and VPL –> cortex –> internal capsule via corticospinal tract or rubrospinal tract–> decussation in medulla –> spinal cord
since there are two decussation sites, damage to right dentate nucleus will cause ipsilateral body effects
What is cerebellar learning?
What are the different waves during BAER monitoring?
Nuclei of CN3, type of efferents, and their targets:
Edinger–Westphal nucleus provides parasympathetic (general visceral efferent)
The general somatic efferents arise from the central nucleus supplying levator palpebrae superioris bilaterally
medial nucleus supplying contralateral superior rectus
lateral nucleus supplying ipsilateral inferior rectus, inferior oblique and medial rectus
