Neurology7-11 Flashcards
Pathogenesis:
Tetrodotoxin (Pufferfish neurotoxin)
- Bind to voltage-gated sodium channels (nerve & cardiac tissue)
- Prevent sodium influx and depolarization
Clinical Manifestation:
Pufferfish poisoning
- Weakness, dizziness & parasthesia in face and extremities
- Reduced muscle strength
- Decreased deep-tendon reflexes
…after eating fish (maybe at a Japanese restaurant)
Treatment
Your patient is witnessed to have jerking movements of the right arm. She does not remember the episode, but her mother reports that she had “bizzare chewing and sucking moments”.
Treat with carbamazepine.
This is a complex partial seizure. The girl has a postictal state (“comples” loss or memory/lethargy) and only one area of her body is involved (“partial”). Carbamazepine can be used to treat: (1) simple partial (2) complex partial & (3) tonic-clonic seizures.
Clinical Manifestation:
Vitamin B deficiency
- loss of position and vibration sense
- ataxia
- spastic paresis
Myelopathy associated with vitamin B deficiency is often referred to as subacute combined degeneration. What does “combined” refer to?
degenerationfo both the ascending (dorsal column) and ddescending (corticospinal tract) pathways
Pathogenesis:
hearing loss due to prolonged exposure to loud noise
stereociliated hair cells in the organ of Corti become damaged
What is the most common extracranial neoplasm in children?
Neuroblastoma
Adrenal medulla tumor in children
Describe the axonal reaction.
- Neuron body is severed
- Large, round cells with peripherally located nuclei with finely dispersed granular Nissl substance can be seen.
Diagnosis:
Congo red staining of brain samples display patchy amyloid deposition in: (1) temporal cortex and hipposcampus & (2) cerebral arterioles
Alzheimer disesase
Amyloid in brain parenchyma=senile plaques
Amyloid in cerebral arterioles=amyloid angiopathy
What additional drug might you prescribe to a Parkinson patient, currently on levodopa/carbidopa, but still experiencing stiffness?
Entacapone
Entacapone is a COMT inhibitor it decreases peripheral metabolism of levodopa. Tolcapone is also a peripheral AND central COMT inhibitor, but it is hepatotoxic.
Why does the axonal reaction occur?
After an axon has been severed, protein synthesis must occur to facilitate the repair process.
Pathogenesis:
Diabetic neuropathy in arteries
- proteins become glycoslated (non-enzymatic)
- Glycosylation results in increased (1) thickness 92) hyalinization and (3) narrowing of the walls
- Ischemic nerve damage follows
These changes lead to diabetic microangiopathy of endoneural arterioles.
Pathogenesis:
Diabetic neuropathy in peripheral nerves
- Intracellular hyperglycemia occurs
- Accumulating glucose is converted inot sorbitol and fructose by aldose reductase
- Sorbitol increases the cellular osmolarity and leads to influx of water
- Osmotic damage to the axons and schwann cells occurs
Clinical Manifestation:
Vernet (jugular foramen) syndrome
Dysfunction of CN IX, X & XI
No taste from posterior 1/3 of tongue (9), Decreased parotid gland secretions (9), Loss of gag reflex (9, 10), Difficulty swallowing (9, 10), dysphonia/hoarseness (10), soft palate drop with uvula deviation towards normal side (10), weakness of the sternocleidomastoid and trapezius muscle (11)
Diagnosis:
Patient exhibits involuntary flinging movements of one side of the body
Hemiballism
A lesion has occurred in the subthalamic nucleus (part of the basal ganglia). The lesion is contralateral to the symptomatic side.
Which cerebral artery results in (1) contralateral motor and sensory deficits of the lower extremities (2) behavior changes & (3) urinary incontinence
anterior cerebral artery
This artery supplies the medial portions of the 2 hemispheres.
Diagnosis:
MRI shows an intracranial calcified mass in a patient complaining of chronic headaches and visual changes
Craniopharyngioma
Clinical Manifestation:
Craniopharyngioma
- headaches
- growth failure
- bitemporal hemianopia
Difference between (1) True hydrocephalus and (2) Hydrocephalus ex vacuo
True hydrocephalus is associated with (1) ventricular enlargement and (2) Increased CSF pressure
Hydrocephalus ex vacuo is associated with (1) Ventricular enlargment and (2) cortical atrophy, BUT IT IS NOT CAUSED BY AN INCREASE IN CSF
Common neurological sequelae of advanced HIV infection
hydrocephalus ex vacuo secondary to cortical atrophy
compensatory ventricular expansion seen in advanced HIV infection
hydrocephalus ex vacuo (secondary to cortical atrophy)
Most common cause of hydrocephalus
obstruction in either the ventricles or arachnoid villi
Where is CSF produced?
choroid plexus
Where is CSF absorbed?
Granulations of the arachnoid matter
Where does CSF circulate?
CSF circulates in the ventricular system and the arachnoid space
Treatment:
Prevention of cerebral vasospasm in patients with subarachnoid hemorrhage (SAH)
Nimodipine (this is an alternative use!)
MA: Calcium channel blocker that prevents cerebral vascular spasm
Clinical Manifestation:
Cerebral vasospasm
- altered mental status
- focal neurological deficits
3- 8 days following subarachnoid hemorrhage; most frequently 7-8 days following SAH
Pathogenesis:
Cerebral vasopasm secondary to subarachnoid hemorrhage (SAH)
unknown mechanism; believed to be the result of subarachnoid blood clot degradation
Treatment:
Maple syrup urine disease (MSUD)
high-dose thiamine treatment + lifelong dietary restrictions
Dietary restrictions are not need in the minority of MSUD patients.
Which enzymes share the same required coenzymes as branched chain alpha ketoacid dehydrogenase?
- Pyruvate dehydrogenase
- Alpha-ketoglutarate dehydrogenase
All require “Tender loving care for Nancy”. Thiamine pyrophosphate, lipoate, coenzyme A, FAD, NAD
List the 5 coenzymes required for the activity of branched chain alpha-ketoacid dehydrogenase
- Thiamine pyrophosphate
- Lipoate
- Coenzyme A
- FAD
- NAD
“Tender loving care for Nancy.”
Pathogenesis:
Maple syrup urine disease
- mutation in any of the 4 genes that code for the 3 subunits of branched-chain alpha-ketoacid dehydrogenase
- Dysfunctional Branch-chain alpha-ketoacid dehydrogenase results in the inability to metabolize branched chain amino acids (i.e. Valine, leucine, isoleucine).
3a. Accumulation of leucine in serum and brain tissue causes neurotoxicity.
3b. Accumulation of isoleucine gives urine distinctive sweet odor.
Clinical Manifestation:
Maple syrup urine disease (MSUD)
- Vomiting
- Irritability
- Lethargy
- Urine smells like “burned sugar/caramel”
in newborn.
Pathogenesis:
Why do patients with maple syrup urine disease exhibit signs of neural dysfunction?
Leucine accumulates in the serum and brain tissues
Pathogenesis:
Why do patients with maple syrup disease have a sweet smelling urine?
A metabolite of isoleucine accumulates in the urine.
What type of dietary restriction might be suggested for a newborn with maple syrup urine disease (MSUD)?
The diet needs to be free from any branched chain amino acids. There are three: Valine, Leucine & Isoleucine.
How does the arteriovenous concentration gradient affect the onset of action of an anesthetic agent?
Large arteriovenous concentration gradient indicates large peripheral tissue solubility and thus a slower onset of action. More inhaled gas is needed to replace gas dissolved into the tissues (you need to saturate the blood).
A small arteriovenous concentration gradient indicates little peripheral tissue solubility and a faster onset of action. Less inhaled gas is need to saturate the blood.
What pathway must an anesthetic agent take to reach the brain?
inspired air –> lungs –> blood –> brain
How is the potency of an anesthetic determined?
Minimal alveolar concentration (MAC)
A high MAC indicates low potency.
List the five (5) causes of polyhydraminos?
- Increased fetal urination (high CO due to anemia (parvovirus) twin-to-twin transfusion syn.)
- Impaired swallowing (GI obstruction due to esophageal, duodenal or intestinal atresia)
- Anencephaly
- Maternal diabetes (mild polyhydraminos)
- Multiple gestations (mild polyhydraminos)
Why is valproate contraindicated in pregnant women?
Valproate is teratogenic and can lead to neural tube defects (i.e. meningocele)
Mechanism of Action:
Valproate in pregnant women during the first trimester
- Valproate inhibits intestinal absorption of folic acid
- Decrease folic acid leads to increased risk for neural tube defects
By what mechanism does Huntington disease alter gene expression of neurotrophic factors?
Histone deacetylation
Hypo-acetylated histones bind DNA tightly and prevent gene transcription.
What is the most common finding in a patient with posterior cerebral artery stroke?
contralateral homonymous hemianopia with macular sparing
Which cranial nerves are supplied by the posterior cerebral artery?
CN III
CN IV
Who is more likely to suffer from a cluster headache? Males or Females?
Males
Clinical Manifestation:
Cluster headache
- severe and episodic
- unilateral periorbial and temporal pain
Cluster headaches may also be associated with: (1) lacrimation (2) nasal congestion & (3) ptosis
Where does the trigeminal nerve exit the brainstem?
at the level of the middle cerebral peduncle along the lateral aspect of the mid-pons
Treatment:
Complex partial seizures
Carbamazepine
Carbamazepine is also effective in generalized tonic-clonic seizures; however, beward of agranulocytosis (aplastic anemia)!
Treatment:
Absence seizures
Ethosuximide
If the patient also has tonic-clonic seizures use sodium valproate instead. Ethosuximide blocks the T-type calcium channels in the thalamic neuron.
Treatment:
child with (1) tonic clonic seizures & (2) absence seizures
Sodium valproate
Clinical Manifestation:
Parasagittal meningioma
Spastic paresis of the contralateral leg due to compression of the leg-foor motor area.
Where is the vomitting center that is stimulated by acute nausea?
The area postrema of the dorsal medulla.
Acute nausea, which can result after chemotherapy has been administered systemically, will stimulate the chemoreceptor trigger zone, which is near the fourth ventricle.
Where does blood accumulate when one tears the middile meningeal artery?
Epidural space
This is common in patients who fracture the temporal bone. They usually present with a “lucid interval” followed by loss of consciousness.
The posterior pituitary is a derivative of which embryologic layer?
Ectoderm
The ectoderm gives rise to the (1) surface ectoderm, (2) neural tube & (3) neural crest. The posterior pituitary is a derivative fo the neural tube.
Treatment:
Alcohol withdrawal
Benzodiazepines. Benzo’s act on the GABA receptors, just like alcohol.
When hospitalized, alcoholics typically develop delirium tremens on the third day of hospitalization.
Diagnosis:
Your patient has a uncomfortable sensation in his leg when at rest or sleeping. The sensation produces an urge to move/stretch the leg
Restless leg syndrome
Treatment: Dopamine agonists.
Schwann cells are embryological derivatives of this structure.
neural crest
Alternative disease name for Recklinghausen’s disease
Neurofibromatosis Type I (NF1)
Pathogenesis:
Right homonymous hemianopia with macular sparing
- Infarction/occlusion of the posterior cerebral artery
- Lesion occurs in the left occipital cortex
How can you determine if a patient with Myasthenia Gravis is being undertreated (Tx: cholinesterase inhibitors)?
Edrophonium (Tensilon) test
If the patient responds they are having a myasthenic crisis and need to have their medications increase. If the patient does not respond they are having a cholinergic crisis and the cholinesterase inhibitors should be discontinued.
How is arginine used in the urea cycle?
Arginine is converted into urea via the enzyme arginase. Arginase accomplishes this by breaking arginine down into (1) ornithine and (2) urea.
Clincal Manifestation:
Arginase deficiency
- spastic paresis
- choreathoid movements
- elevated arginine in the CSF and plasma
Argniase deficiency is often underdiagnosed because it presents similar to cerebral palsy.
Treatment:
Orotic aciduria (impaired de novo pyrimidine synthesis)
Uridine
Urindine is converted to UMP which inhibits carbamoyl phosphate synthetase II. This is the first enzyme, and the regulatory step or pyrimidine synthesis. If you inhibit this step you will not build up orotic acid.
Clinical Manifestation:
- hypochromic megaloblastic anemia
- neurologic abnormalities
- growth retardation
- elevated orotic acid urine
Orotic aciduria (impaired de novo pyrimidine synthesis)
Pathogenesis: Defective orotate phosphoribosyl transferase and OMP decarboxylase
