Disorders of the Nervous System Caused by Alcohol, Drugs, Toxins, and Chemical Agents

Flashcards covering Chapter 41: Disorders of the Nervous System Caused by Alcohol, Drugs, Toxins, and Chemical Agents from Adams and Victor's Principles of Neurology, 12th Edition.

Who originally enunciated the principle of selective vulnerability under the concept termed pathoclisis?

Oskar and Cecile Vogt.

Which synthetic neurotoxin causes a selective progressive loss of melanin-bearing dopaminergic nigral neurons?

1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP).

Baclofen modulates the release of which primary inhibitory neurotransmitter in the central nervous system?

Gamma-aminobutyric acid (GABA).

How do botulinum toxin and tetanus toxin differ in their target sites of neurotransmitter inhibition?

Botulinum toxin prevents acetylcholine release at the neuromuscular junction, whereas tetanus toxin prevents GABA release in Renshaw cells of the spinal cord.

According to U.S. Department of Health and Human Services figures cited in the text, what percentage of medical and surgical patients have alcohol-related problems?

Up to $40\%$ of medical and surgical patients.

What percentage of fatal motor vehicle accidents in the United States involves alcohol intoxication?

Approximately $45\%$.

Which primary enzyme system accounts for 80 to 90 percent of ethanol oxidation in vivo?

Alcohol dehydrogenase (ADH) and its isoenzymes.

Which enzyme converts acetaldehyde into acetate during alcohol metabolism?

Aldehyde dehydrogenase.

Deficiency of which enzyme activity causes the flushing reaction after alcohol ingestion in many Asian individuals?

Aldehyde dehydrogenase.

According to Miles' scale for nonhabituated persons, what blood alcohol level corresponds to obvious ataxia?

$$100\,mg/dL$$

On Miles' scale, at what blood alcohol concentration is deep anesthesia present and potentially fatal?

$$400\,mg/dL$$

Once equilibrium is established after absorption, at what rate is ethanol oxidized in the body?

At a constant rate of about $150\,mg$ alcohol per kilogram of body weight per hour (or about $1\,oz$ of 90-proof whiskey per hour).

How does disulfiram produce adverse symptoms when combined with alcohol?

It raises tissue concentrations of acetaldehyde by inhibiting its oxidation, causing nausea, vomiting, and severe hypotension.

What effect does chronic administration of alcohol have on neuronal membrane ion channels according to Dolin and Little?

It increases the number of neuronal calcium channels in the cell membrane.

What defining memory impairment characterizes an alcoholic blackout?

An impairment of short-term (retentive) memory during severe intoxication, resulting in amnesia for the interval without gross alteration of consciousness.

Why are analeptic drugs such as amphetamine, caffeine, or picrotoxin not clinically useful in severe alcohol intoxication?

They act only as overall nervous system excitants and do not hasten the rate of alcohol oxidation.

At what blood alcohol threshold is hemodialysis considered for comatose patients?

Blood alcohol concentrations greater than $500\,mg/dL$.

What characteristic organ damage and brain lesion pattern occur in severe methyl alcohol (methanol) poisoning?

Retinal ganglion cell damage (causing scotomata and blindness) and bilateral putaminal degeneration.

What primary treatment is administered intravenously to reverse severe metabolic acidosis in methanol poisoning?

Large amounts of sodium bicarbonate.

What toxic metabolic product of ethylene glycol causes metabolic acidosis and renal failure?

Glycolic acid, which leads to the formation and renal deposition of calcium oxalate crystals.

Why is 4-methylpyrazole (fomepizole) preferred over ethanol in treating ethylene glycol and methanol poisoning?

It is a more effective inhibitor of alcohol dehydrogenase (ADH) and avoids the complex dosing and side effects associated with ethanol administration.

What delayed neurological deficit appearing 6 to 18 days after ethylene glycol ingestion is attributed to oxalate crystal deposition?

Multiple cranial nerve defects, particularly affecting the seventh and eighth cranial nerves.

What is the most common single manifestation of the alcohol abstinence syndrome, and when does it reach peak intensity?

Tremulousness (the shakes), reaching peak intensity 24 to 36 hours after complete cessation of drinking.

Based on the image below illustrating alcohol withdrawal disturbances, what is the peak onset time range for withdrawal fits (seizures)?

Between 13 and 24 hours (1 day) after cessation of drinking.

What percentage of alcohol withdrawal seizures occur within the 7- to 48-hour period following cessation of drinking?

More than $90\%$.

What stroboscopic EEG response is seen in almost half of patients during the alcohol withdrawal seizure period?

A photoparoxysmal response (generalized myoclonus or a convulsive seizure).

What clinical feature distinguishes acute alcoholic auditory hallucinosis from schizophrenia during the withdrawal period?

Patients have an otherwise clear sensorium (they are not disoriented or obtunded) and possess an intact memory.

What was the historical mortality rate of delirium tremens compared to the modern mortality rate?

Approximately $15\%$ in the past, compared to closer to $5\%$ currently.

What electrolyte and acid-base disturbances typically accompany the early phase of alcohol withdrawal?

Hypomagnesemia (low serum magnesium) and arterial alkalosis (high arterial pH due to respiratory alkalosis).

Why must thiamine be administered whenever intravenous glucose solutions are given to alcoholic patients?

Administering glucose alone can rapidly consume remaining thiamine reserves and precipitate acute Wernicke disease.

Neuropathologic examination of brains from patients clinically labeled with alcoholic dementia most commonly reveals which underlying lesions?

Lesions of the Wernicke-Korsakoff syndrome.

What distinctive facial anomalies characterize infants born with Fetal Alcohol Syndrome (FAS)?

Short palpebral fissures, epicanthal folds, maxillary hypoplasia, micrognathia, an indistinct philtrum, and a thin upper lip.

According to Ikonomidou et al., by what cellular mechanism does alcohol exposure delete millions of neurons in the developing brain?

Apoptosis (programmed cell death) during synaptogenesis.

Which oral opioid antagonist medication is utilized to manage alcohol dependence and reduce relapse?

Naltrexone.

What is the therapeutic mechanism of disulfiram in maintain sobriety in alcohol use disorder?

It blocks aldehyde dehydrogenase, causing a severe accumulation of toxic acetaldehyde if alcohol is ingested.

Which three primary opioid receptor types mediate opioid actions in the nervous system?

Mu ($\mu$), delta ($\delta$), and kappa ($\kappa$) receptors.

What classic triad of signs characterizes acute opioid poisoning?

Unresponsiveness (coma), pinpoint pupils (miosis), and slow, shallow respiration.

What specific pure opioid antagonist is the drug of choice for acute opioid overdose?

Naloxone (Narcan).

What is the recommended initial intravenous dose of naloxone for acute opioid overdose in adults?

$0.4\text{ to }0.5\,mg$, repeated in larger increments up to $15\,mg$ if required.

At what time point after morphine withdrawal do the physical signs of the abstinence syndrome reach peak intensity?

48 to 72 hours after withdrawal.

Why is methadone suitable for detoxification and maintenance in heroin dependence?

It is long-acting, effective orally, and produces a milder, more slowly developing abstinence syndrome.

What sublingual combination containing a partial opioid agonist and antagonist is widely used for office-based opioid dependence treatment?

Buprenorphine and naloxone.

Inhalation of heated heroin vapor ("chasing the dragon") can cause what severe white matter brain disorder?

Spongiform leukoencephalopathy (subacute progressive cerebral leukoencephalopathy).

By what primary mechanism do barbiturates suppress neuronal transmission in the central nervous system?

By enhancing GABA inhibition at pre- and postsynaptic receptor sites and reducing excitatory postsynaptic potentials.

What pattern of pupillary response and reflexes is present in deep barbiturate-induced coma?

Flaccid coma with small, reactive pupils (unless asphyxiated) and absent corneal, gag, and tendon reflexes.

When do generalized withdrawal seizures typically occur after cessation of chronic short- or intermediate-acting barbiturate use?

Between the second and fourth days of abstinence.

What specific competitive antagonist rapidly reverses benzodiazepine-induced central nervous system depression?

Flumazenil.

How does buspirone differ pharmacologically from benzodiazepines and barbiturates?

It is a selective 5-HT1A serotonergic receptor agonist and does not act on GABA receptors or block withdrawal from other sedatives.

Through what primary receptor blockade do standard antipsychotic drugs exert both their therapeutic effects and parkinsonian side effects?

Blockade of postsynaptic mesolimbic and striatal dopamine D2 receptors.

What four main extrapyramidal motor syndromes are associated with neuroleptic drug use?

Parkinsonian syndrome, acute dyskinetic/dystonic reactions, akathisia, and tardive dyskinesia.

What acute intervention terminates acute neuroleptic-induced dystonic spasms?

Discontinuation of the drug and immediate intravenous administration of diphenhydramine hydrochloride or benztropine.

What are the cardinal clinical manifestations of Neuroleptic Malignant Syndrome (NMS)?

Hyperthermia, muscle rigidity, stupor, autonomic instability (unstable blood pressure, diaphoresis), and markedly elevated serum creatine kinase (CK).

Which two specific medications are indicated for treating Neuroleptic Malignant Syndrome?

Bromocriptine (a dopamine agonist) and dantrolene (a skeletal muscle relaxant).

Why must patients taking Monoamine Oxidase (MAO-A) inhibitors avoid tyramine-containing foods like aged cheese and red wine?

Inhibition of intestinal and hepatic MAO-A allows dietary tyramine to enter the systemic circulation and release norepinephrine, causing a severe hypertensive crisis.

What is the mode of action of tricyclic antidepressants?

They block the presynaptic reuptake (transporter) of amine neurotransmitters, specifically norepinephrine and serotonin.

What is the primary cause of mortality in tricyclic antidepressant overdose?

Cardiac rhythm disturbances (tachyarrhythmias) and impaired atrioventricular conduction.

What clinical features characterize the serotonin syndrome resulting from SSRI toxicity or drug interactions?

Confusion, restlessness, tremor, tachycardia, hypertension, clonus, hyperreflexia, shivering, and diaphoresis.

Which 5-HT2A receptor blocker is administered in severe cases of serotonin syndrome?

Cyproheptadine.

What is the normal therapeutic serum level range for lithium in managing bipolar disorder?

$$0.6\text{ to }1.2\,mEq/L$$

What neurological symptoms indicate lithium toxicity at serum levels above 1.5 to 2 mEq/L?

Confusion, delirium, ataxia, vertical downbeating nystagmus, opsoclonus, stammering, and diffuse myoclonic twitching.

How do amphetamines exert their central nervous system stimulant actions?

By promoting the release of endogenous catecholamines from presynaptic nerve terminals.

What primary mechanism accounts for the pharmacological and addictive effects of cocaine?

Blockade of presynaptic reuptake of biogenic amines (dopamine, norepinephrine, serotonin).

What severe cerebrovascular complications are associated with acute cocaine or amphetamine abuse?

Subarachnoid hemorrhage, intracerebral hemorrhage, ischemic stroke, and posterior reversible encephalopathy syndrome (PRES).

Which brain receptor is activated by marijuana and delta-9-tetrahydrocannabinol?

The CB1 cannabinoid receptor, located mainly on GABA-ergic neurons.

What enzymatic activity does tetanus toxin possess, and which spinal cell type does it preferentially affect?

It is a zinc-dependent protease that cleaves synaptic vesicle proteins, selectively blocking GABA release from Renshaw cells.

What electromyographic (EMG) abnormality is characteristic of tetanus?

Loss of the normal physiologic silent period ($50\text{ to }100\,ms$) following reflex muscle contraction.

What initial symptom is most characteristic of generalized tetanus?

Trismus (lockjaw) due to involuntary contraction of the masseter muscles.

What classic biphasic pattern of neurological involvement occurs in faucial diphtheria?

Early palatal and cranial nerve paralysis (days 5 to 12), followed weeks later (weeks 5 to 8) by a delayed, symmetrical sensorimotor polyneuropathy.

What is the presynaptic mechanism of action of botulinum toxin?

It blocks the presynaptic release of acetylcholine at neuromuscular junctions and parasympathetic synapses.

What electrophysiologic response on rapid repetitive nerve stimulation distinguishes botulism from myasthenia gravis?

An increase (facilitation) in muscle action potential amplitude with rapid repetitive nerve stimulation.

What neurological condition is caused by Lathyrism (consumption of chickling vetch pea)?

A permanent spastic paraplegia resulting from spinal cord damage.

What organ damage and neurological signs follow poisoning by Amanita phalloides mushrooms?

Disruption of RNA metabolism causing hepatic and renal necrosis, accompanied by ataxia, hallucinations, convulsions, and neuromyopathy.

What sensory symptom is characteristic of Ciguatera marine fish poisoning?

Temperature reversal paresthesias (where cold objects elicit burning or electrical sensations).

Which tick species in North America are most commonly responsible for tick paralysis?

Dermacentor andersoni (wood tick) and Dermacentor variabilis (dog tick).

What is the definitive treatment for tick paralysis, and how quickly does recovery occur?

Search for and removal of the attached tick, leading to rapid recovery within hours or days.

What clinical features characterize acute lead encephalopathy in young children?

Severe brain swelling with papilledema, persistent vomiting, apathy, seizures, and coma, frequently leaving permanent cognitive deficits.

What classic peripheral nerve manifestation occurs in adult lead intoxication?

Bilateral motor neuropathy presenting as wrist drop.

What fingernail abnormality (Mees lines) is associated with chronic arsenic poisoning?

Transverse white lines, 1 to 2 mm in width, located above the lunula of each fingernail.

What specific histopathology was identified in Minamata disease (methylmercury poisoning)?

Degeneration of the granular layer of the cerebellar cortex (sparing Purkinje cells) and neuronal loss in the calcarine (visual) cortex.

Look at the MRI image below. What condition is shown in this axial T2-FLAIR brain scan, and which antineoplastic or immunosuppressive drugs cause it?

Posterior Reversible Encephalopathy Syndrome (PRES / Toxic Reversible Posterior Leukoencephalopathy), commonly caused by calcineurin inhibitors (cyclosporine, tacrolimus) and agents like methotrexate, vincristine, cisplatin, and L-asparaginase.

What central concept of neurotoxicology, originally enunciated by Oskar and Cecile Vogt under the term pathoclisis, describes how specific neuronal systems possess unique vulnerabilities to particular drugs and toxins?

Selective vulnerability

Which specific population of neurons is selectively destroyed by the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) to produce parkinsonism?

Melanin-bearing dopaminergic nigral neurons

Which anatomical structure in the brainstem contains neurons preferentially affected by general anesthetics?

Upper brainstem reticular formation

According to figures from the US Department of Health and Human Services, what percentage of medical and surgical hospital patients have alcohol-related problems?

Up to $40\%$

What minimum percentage of all deaths in the United States is directly attributable to alcohol-related causes?

A minimum of $3\%$

Alcohol intoxication is involved in approximately what percentage of fatal motor vehicle accidents in the United States?

Approximately $45\%$

What percentage of fatal boating accidents involves alcohol intoxication?

$$22\%$$

What primary enzyme system in the liver oxidizes $80\text{ to }90\%$ of ethanol in vivo to form acetaldehyde?

Alcohol dehydrogenase (ADH)

Acetaldehyde is converted into acetate primarily by which enzyme?

Aldehyde dehydrogenase

What metabolic enzymatic deficiency accounts for the facial flushing reaction observed in many Asian individuals after alcohol ingestion?

A deficiency of aldehyde dehydrogenase activity

According to Miles' scale of functional impairment, what clinical effect is detectable at a blood alcohol level of $30\,mg/dL$ in nonhabituated individuals?

Mild euphoria

At what blood alcohol concentration is obvious ataxia typically present in a nonhabituated person?

$$100\,mg/dL$$

According to Miles' scale, what degree of functional impairment occurs at a blood alcohol level of $300\,mg/dL$?

Subjects become stuporous

What blood alcohol concentration in a nonhabituated person produces deep anesthesia and is potentially fatal?

$$400\,mg/dL$$

At what constant rate is ethanol oxidized in the body once absorption and tissue equilibrium are established?

About $150\,mg$ alcohol per kilogram of body weight per hour (or about $1\,oz$ of 90-proof whiskey per hour)

What is the biochemical mechanism by which disulfiram causes severe flushing, nausea, vomiting, and hypotension when combined with alcohol?

It raises the tissue concentration of acetaldehyde by blocking its metabolism via aldehyde dehydrogenase

Which membrane receptor and ion-channel complex is heavily implicated in mediating the acute intoxicating effects of alcohol via potentiated chloride flux?

GABA-A receptor and its associated chloride-ion channel

Which major excitatory neurotransmitter receptor in the brain is sensitive to inhibition by extremely low concentrations of alcohol?

N-methyl-D-aspartate (NMDA) receptor

How does chronic administration of alcohol alter neuronal calcium channels in the cell membrane?

It increases the number of neuronal calcium channels

What is meant by the term pathologic intoxication (or atypical/idiosyncratic alcohol intoxication)?

An episode characterized by an outburst of blind fury with assaultive and destructive behavior following alcohol consumption, terminating in deep sleep and amnesia for the event