Neurotransmitters and Receptors
Which of the following is implicated as the most likely pathophysiology in patients with depression?
A. Increased dopamine
B. Decreased serotonin
C. Increased norepinephrine
D. Increased gamma-aminobutyric acid (GABA)
E. Decreased acetylcholine
what is
B. Decreased serotonin
Explanation:
Decreased serotonin is the correct answer because the use of selective serotonin reuptake inhibitors (SSRIs) have shown improvement in symptoms of depression. Several studies have shown that decreased levels of serotonin may precipitate depression. Also, decreased levels of serotonin metabolites have been noted in the cerebrospinal fluids of patients with suicidal ideation indicating the involvement of serotonin in the pathophysiology of depression. Increased dopamine is incorrect because studies have shown that decreased levels of dopamine are associated with depressive symptoms. Also, studies have shown that the mesolimbic dopaminergic pathway may be impaired along with hypoactivity of D1 receptors in patients diagnosed with depression. Increased norepinephrine is incorrect because according to the monoamine hypothesis, antidepressants work by inhibiting the reuptake of norepinephrine or antagonize presynaptic inhibitory norepinephrine receptors resulting in enhanced neurotransmission of norepinephrine. Increased gamma-aminobutyric acid (GABA) is incorrect because decreased levels of GABA have been demonstrated in plasma, cerebrospinal fluid, and brain in patients diagnosed with depression. Decreased levels of acetylcholine is incorrect because the use of cholinergic agonists results in exacerbation of the depressive symptoms.
This vitamin deficiency is linked with the pathophysiology of restless leg syndrome.
- vitamin B12
- vitamin E
- vitamin A
- iron
- thiamine
What is iron deficiency.
Restless leg syndrome is associated with iron deficiency. There is a decreased availability of iron in the neuromelanin cells of the substantial Nigra, which leads to reduced activity of the enzyme involved in the dopamine synthesis or reduced expression of dopamine receptors and transporters. Studies have shown decreased levels of ferritin in the cerebrospinal fluid as compared to normal plasma levels that suggest specific brain iron deficiency impatience with RLS. Under imaging, there is decreased density of D2 dopamine receptors in the striatum.
A 43-year-old man presents with complaints of an abnormal "crawling" sensation in his legs when he goes to bed. His partner notices intermittent movements of his lower extremities approximately every minute. Which one of the following medications is most likely to improve his symptoms?
A. Ropinirole
B. Phenobarbital
C. Verapamil
D. Intravenous immunoglobin
E. Paroxetine
what is
A. Ropinirole
Explanation:
Dopamine agonists are considered first-line agents in the treatment of restless legs syndrome. This patient has symptoms of both restless legs syndrome and periodic limb movements in sleep. Second-line agents for the treatment of RLS include benzodiazepines (clonazepam), opiates, clonidine, carbamezapine, bromocriptine, pregabalin, and baclofen.
Which of the following features is necessary to establish a diagnosis of delirium?
A. Presence of a medical condition
B. Caused by substance intoxication
C. Disturbance in attention
D. Caused by substance withdrawal
E. Induced by a medication
what is
C. Disturbance in attention
Explanation:
According to the DSM-V, diagnosis of delirium is made when there is a disturbance in attention and awareness. This disturbance can manifest as a decreased ability to direct, focus, sustain, and shift attention as well as reduced orientation towards the surroundings. The development of this disturbance is over a short period of time from hours to a few days. There must be a change in the baseline attention and awareness to constitute as delirium, and fluctuations in the severity of attention and awareness can occur over the course of the day. There is a possibility of other disturbances in cognition to be present as well, for example, lapses in memory, visuospatial disturbances, inability to communicate, and disturbances in perception. The cause of delirium can be due to a medical condition, substance intoxication or withdrawal (either from medication or use of an illicit drug), exposure to a toxin, or due to several etiologies combined.
A 21-year-old man sustains a traumatic brain injury while a passenger in a motor vehicle. As a consequence his ability to plan, sequence and monitor his activities for effectiveness is impaired. His cognitive dysfunction is best characterized as which of the following?
A. Acalculia
B. Agnosia
C. Executive dysfunction
D. Simultagnosia
E. Personality change due to brain injury
what is
C. Executive dysfunction
Explanation:
The correct response is executive dysfunction. Executive function encompasses a wide range of cognitive skills that allow us to plan, organize, and sequence our thoughts and information to help us make decisions and solve problems in our daily lives. It enables us to grasp information in our working memory, control our inhibitions and shift and focus our attention flexibly, supported by the pre-frontal cortex. Impairment in executive functioning manifests as an inability to solve complex problems or perform difficult, multistage projects. Multi-tasking becomes difficult because planning, organizing and sequencing to make any decision require more effort and energy, which can be seen in this case. Acalculia is the inability to perform calculations. Agnosia is the inability to recognize a sensory stimulus; this can be in the form of an object, person, sound or shape. For example, simultanagnosia is an impairment in the perception of more than one object at a time. Traumatic brain injury can also lead to changes in personality, where patients may become apathetic, paranoid, disinhibited, aggressive or hypersexual, which is not seen in this case.
Which of the following neurotransmitters is associated with hypersomnia?
A. γ-Aminobutyric acid
B. Serotonin
C. Norepinephrine
D. Dopamine
E. Acetylcholine
what is
A. γ-Aminobutyric acid
Explanation:
GABA (γ-aminobutyric acid) is the major inhibitory neurotransmitter in the brain. Activation of GABA-A receptors results in an increase in the neuronal inhibition by increasing chloride ion conductance leading to increased sleep and sedation. Serotonin is involved in the wakefulness and decrease in sleep when serotonin receptors are activated in the dorsal raphé nucleus and preoptic area. Serotonin inhibits rapid eye movement (REM). Norepinephrine release by the neurons of the locus ceruleus causes an inhibition of rapid eye movement sleep, promotes wakefulness, and stimulate other regions of the brain associated with aroused state including the hypothalamus, thalamus, basal forebrain, and cortex Dopamine is associated with regulation of wakefulness through signalling from the ventral tegmental area to the dorsal raphé nucleus, basal forebrain, locus coeruleus, thalamus, and laterodorsal tegmental nucleus, ventrolateral periaqueductal gray that are active during wakefulness. Acetylcholine plays an important role in wakefulness and REM sleep, and is at its lowest level during non-REM sleep. Acetylcholine released from the neurons of laterodorsal tegmental and pedunculopontine tegmental nuclei (LDT/PPT) and the basal forebrain stimulate the neocortex during both wakefulness and REM sleep
A 33-year-old woman presents with a history of four headaches with gradually developing visual symptoms (described as bright zigzags), unilateral sensory symptoms, and no motor weakness. Which one of the following is considered the drug class of choice for abortive therapy of her condition?
A. Triptans
B. IV antiemetics
C. Ergotamine
D. NSAIDs
E. Benzodiazepines
A. Triptans
Explanation:
Triptans (SC, PO, and intranasal) are now considered the drug class of choice for abortive therapy of migraine headaches. Meta-analyses suggest that 10 mg rizatriptan, 80 mg of eletriptan, and 12.5 mg of almotriptan are the most effective. Early administration has been shown to improve effectiveness. Ergotamines and NSAIDs may also be used for abortive therapy, but triptans are considered the treatment of choice.
This class of drugs would be the most likely to cause neuroleptic malignant syndrome.
-SSRIs
-SNRIs
-anticonvulsants
-antipsychotics
What are antipsychotic drugs.
NMS is a life threatening neurological disorder that is often used by and adverse reaction to neuroleptic or antipsychotic drugs. Symptoms typically include high fever sweating unstable blood pressure stupor muscular rigidity, an autonomic dysfunction. Typically animals developed within the first 2 weeks of treatment with the drug; However the disorder may develop anytime during the therapy. The syndrome may occur in patients taking dopaminergic's if they are discontinued abruptly. Generally intensive care is needed for proper treatment. The neuroleptic or antipsychotic drug is discontinued and the fever is treated aggressively.
A 78-year-old man, a diagnosed case of major neurocognitive disorder due to Alzheimer's disease, is brought for evaluation of anxiety, restlessness, and irritability that has been present for the past 6 months but has worsened for the past week. There is associated insomnia and poor fluency in the language. Currently, the patient appears acutely agitated, aggressive, and furious. He gets out of control during consult, starts shouting and attacking nursing staff in an agitated manner. For what condition is the use of benzodiazepine warranted in this patient?
A. Alzheimer's disease
B. Anxiety
C. Insomnia
D. Delirium
E. Acute agitation
what is
E. Acute agitation
Explanation:
The major neurocognitive disorder due to Alzheimer's disease comprises of severe cognitive decline and behavioral disturbances. The use of benzodiazepines is not recommended in patients with Alzheimer's disease because of three primary reasons. Firstly, due to advanced age the patients are more prone to falls and accidents under the influence of benzodiazepines. Secondly, chronic benzodiazepine use has been documented to cause worsening of cognitive functions in Alzheimer's disease, so their use is best avoided in chronic conditions. Thirdly, benzodiazepines can precipitate delirium and can cause aspiration pneumonia from altered arousal especially in elderly with dementia. There are particular conditions in which the use of benzodiazepines is warranted in patients with Alzheimer's and the principal one is acute agitation in an emergency setting. In such cases, a measured dose of lorazepam is allowed for temporary use to control the severe agitation and aggression in patients with Alzheimer's. Lorazepam is the most common agent permitted because of its short half-life, predictable bioavailability, rapid clearance, and no active metabolites. Benzodiazepines are not recommended in the setting of delirium because they worsen cognition and make the patient prone to further complications. Use of benzodiazepines in elderly with Alzheimer's should be strictly regulated and never prescribed for anxiety, insomnia, delirium, or cognitive complaints. Its use is only justified in an emergency setting, during acute agitation that needs to be addressed immediately before the patient does harm to self or others.
A 72-year-old male patient with cognitive impairment develops frightening visual hallucinations. You prescribe low dose risperidone. The patient develops severe bradykinesia, tremor, rigidity, and gait disturbance. His adverse reaction suggests which NCD diagnosis?
A. NCD due to Alzheimer's disease
B. NCD with Lewy bodies
C. Normal pressure hydrocephalus
D. NCD due to frontotemporal lobar degeneration
E. Vascular NCD
B. NCD with Lewy bodies
Explanation:
The correct response is NCD with Lewy bodies. Dementia with lewy bodies (DLB) is the second most common cause of dementia in the elderly, which is characterized by a progressive decline in cognitive function. Its central features include fluctuating levels of cognition (patients particularly experience great deviations in their level of alertness and attention), visual hallucinations (which are persistent, recurrent and may even be detailed), and motor features of Parkinsonism. Approximately half of the patients with DLB are extremely sensitive to neuroleptic drugs, like risperidone, and the presence of this feature in an individual is highly suggestive of the diagnosis. This hypersensitivity to dopamine 2 (D2) receptor blocking antipsychotics is a result of defective up-regulation of D2 receptors. Even a low dose antipsychotic can exacerbate symptoms of parkinsonism, including rigidity, bradykinesia, shuffling gait, as well as result in somnolence and falls. This hypersensitivity is not a feature of NCD due to Alzheimer's disease, frontotemporal lobar degeneration, vascular NCD or normal pressure hydrocephalus.
Cognitive impairment is frequently observed in patients with schizophrenia. Which of the following neurotransmitter have been implicated for this abnormality?
A. Dopamine
B. Serotonin
C. Norepinephrine
D. Acetylcholine
E. Glutamate
what is
D. Acetylcholine
Explanation:
In patients with schizophrenia experiencing cognitive impairment, there is decreased muscarinic and nicotinic receptors found in the caudate-putamen, hippocampus, and certain regions of prefrontal cortex. These receptors regulate the neurotransmitters that are involved in cognition. Increased dopamine levels have been associated with greater severity of positive symptoms in patients with schizophrenia. Increased activity of serotonin is associated with the production of positive and negative symptoms in patients with schizophrenia. Degeneration of selected norepinephrine neurons results in the symptom of anhedonia, which is a prominent feature of schizophrenia. Decreased levels of glutamate has been implicated in production of an acute syndrome similar to schizophrenia but is not associated with cognitive impairment.
In laboratory studies of patients with acute disseminated the following blood component is most likely to be elevated.
A platelets
B potassium
C hemoglobin
D albumin
E bilirubin
what are platelets
platelet counts are elevated in a substantial number of children with ADEM. Sedimentation rates are occasionally mildly elevated, greater elevation suggests the possibility of vasculitis or infection. Modest moderate elevation of CSF Anne white and red blood cell counts may be found. CSF myelin basic protein concentration, reflecting demyelination is frequently elevated
A 79-year-old female nursing home resident is found unresponsive. Her nephew, who visited that day, is called and admits to giving the patient some 'generic Benadryl' for her allergies. Which medication is most likely to reverse the patient's delirium?
A. Atropine
B. Naloxone
C. Flumazenil
D. Pralidoxime (2-PAM)
E. Physostigmine
what is
E. Physostigmine
Explanation:
Benadryl is an antihistamine made of diphenhydramine and its overdose is treated by giving physostigmine, which is tertiary amine carbamate dose-dependent acetylcholinesterase and butyrylcholinesterase inhibitor in the brain, RBCs and plasma. Due to its unique ability to cross the blood brain barrier (on account of its tertiary amine structure), it is able to reverse the central and the peripheral side effects of anticholinergic toxicity. Its onset of action is 3-8 min after parenteral administration. The cholinergic effects produced by physostigmine give rise to its antidotal properties as well as its adverse effects. These include sweating, increased salivation, visual hallucinations, seizures, possible bronchospasms, increased intestinal peristalsis, and several cardiovascular effects like arrythmias and cardiac arrest. Flumezanil is used to treat benzodiazepine overdose and naloxone is used to treat opioid overdose. Flumezanil also reverses the effects of sedatives that bind at the benzodiazepine receptors like cyclopyrrolone zopiclone. Atropine and pralidoxime are used in organophosphate poisoning.
On autopsy, hyperphosphorylated tau protein found in the hippocampus is most common in which one of the following neurocognitive disorders?
A. Creutzfeldt-Jakob disease
B. Lewy body disease
C. Neurosyphillis
D. Alzheimer's disease
E. Vascular disease
what is
D. Alzheimer's disease
Explanation:
Neurofibrillary changes in the hippocampus are a hallmark of neurocognitive disorder due to Alzheimer's disease. Hyperphosphorylated tau is a characteristic form of tau comprising the neurofibrillary tangles of Alzheimer's disease.
A 56-year-old male has insidious onset of cognitive impairment, depression and rapid jerky movements in his limbs and trunk. His father died from an advanced form of this condition. Which treatment would most likely help to decrease his disabling movement disturbance?
A. Carbidopa/levodopa
B. Fluoxetine
C. Rivastigmine
D. Ropinirole
E. Tetrabenazine
what is
E. Tetrabenazine
Explanation:
The correct response is tetrabenazine. This patient most likely suffers from Huntington's disease (HD), a neurodegenerative disease characterized by progressive motor, psychiatric, and cognitive decline. Psychiatric, behavioral and cognitive changes may occur years before motor abnormalities manifest, and include depression, irritability, apathy, and impulsivity. Chorea, which are irregular jerky movements, mostly affects the limbs and trunk, followed by voluntary motor abnormalities and cognitive decline at a rate of upto 2 points/year on MMSE. It is an autosomal dominant disease, therefore a family history is usually present; in this case, the patient's father suffered from the disease. Although there is no treatment to stop the neurodegeneration, chorea may be effectively treated by tetrabenazine, a vesicular monoamine transporter type-2 inhibitor which blocks dopamine release. Carbidopa/levodopa and ropinirole (D2 agonist) are used to manage symptoms of motor deficits in Parkinson's disease. Rivastigmine, a cholinesterase inhibitor, is used to treat cognitive impairment in Alzheimers and parkinson's disease. Fluoxetine, an SSRI (selective serotonin reuptake inhibitor) may be used to treat this patients depression, not movement disturbance.
Activation of the following opioid receptor subtype is associated with respiratory depression:
A. Delta
B. Kappa
C. Mu
D. ORL
E. OP4
what is mu
Three types of classical opioid receptors exist: µ (mu) or MOR, κ (kappa) or KOR, and δ (delta) or DOR. Another opioid-like receptor which has been identified is nociceptin or orphanin FQ peptide receptor or NOR, which activates the ORL-1 (opioid receptor like-1). The classical receptors are activated by endogenous opioids like encephalins, endorphins and dynorphins, whereas exogenous opioids, like morphine, act mostly on the mu receptors. This makes the mu receptors family most clinically important as the inhibition of nociceptive pathways exploited by the exogenous opioids are the prime responsibility of these receptors. The mu opioid receptors are found in the central and peripheral nervous systems. In the central nervous system, they are found in the brain (cerebral cortex, thalamus, hypothalamus, striatum, amygdala, periaqueductal grey) and in the spinal cord (pre- and post-synaptic neurons). Peripherally, they are found in the pre- and post-synaptic neurons. Their functions include: analgesia, respiratory depression, reduced GI motility, miosis, euphoria, sedation, and physical dependence.
A patient is noted to be very calm, but also is noted to inappropriately put things in their mouth. They are also noted to be overly sexual. The ablation of which area of the brain could produce these symptoms?
A. Anterior cingulate gyri
B. Subcallosal gyri
C. Medial temporal lobe
D. Hippocampus
E. Prefrontal association area
what is
C. Medial temporal lobe
Explanation:
Ablation of the medial temporal lobe causes damage to the bilateral amygdalas as well, leading to Kluver-Bucy syndrome, in which the patient develops excessive tameness as well as hyperphagia, hyperorality and hypersexuality. Ablation of the anterior cingulate gyri and subcallosal gyri leads to increase in viciousness and rage as there is no longer any inhibitory effect on the rage centers. Ablation of the anterior cingulate gyri and subcallosal gyri leads to increase in viciousness and rage as there is no longer any inhibitory effect on the rage centers. Ablation of the hippocampus would result in anterograde amnesia Prefrontal association area helps to plan complex motor movements and sequences of motor movements by working in conjunction with the motor cortex. It is also responsible for higher intellectual functions.
Which one of the following anti-epileptic medications is most often associated with hyponatremia?
A. Phenytoin
B. Carbamazepine
C. Oxcarbazepine
D. Valproic acid
E. Felbamate
What is C. Oxcarbazepine
Explanation:
Risk factors for oxcarbazepine include severe and symptomatic hyponatremia.
A 79-year-old homeless man with alcohol use disorder, hypertension, and hepatitis B is brought into the emergency department by ambulance. He is noted to be tremulous and confused. The physician completes a Clinical Institute Withdrawal Assessment for Alcohol (CIWA). Which one of the following values represents the minimum score at which the physician should be concerned about alcohol withdrawal delirium (delirium tremens)?
A. 10
B. 12
C. 14
D. 16
E. 18
what is
D. 16
Explanation:
The CIWA is an objective assessment tool that can be used to quantify the severity of alcohol withdrawal. The maximum number of points of the CIWA is 67. Mild withdrawal is 8 or less on the CIWA; moderate withdrawal is 9 to 15; and severe withdrawal is 16 and over. Severe withdrawal is associated with DTs and seizures and should be treated aggressively.
A 49-year-old man is an unrestrained driver in a motor vehicle crash. He sustains complicated mild musculoskeletal injuries as well as traumatic brain injury (TBI). Which pre-morbid modifiable risk factor affects his chance of developing post-TBI major depression?
A. Alcohol dependence
B. Depression at time of injury
C. Depression prior to injury
D. Genetic polymorphisms
E. Psychosocial risk factors
what is
A. Alcohol dependence
Explanation:
Risk factors for major depression in the aftermath of TBI are similar to those for endogenous major depression in the general population. Option A is correct since alcoholism is correlated with both increased risk for TBI and depression and is a modifiable risk factor. Options B and C are incorrect because depression is not a modifiable risk factor, and there is some equivocation in the literature concerning the relation of pre-TBI affective disorder to post-TBI depression (though there appears to be a trend toward correlation). Options D and E are both incorrect as there is insufficient evidence at present to draw a correlation. In addition, one's genes are not considered modifiable, and psychosocial variables may not necessarily be modifiable.
A 29-year-old woman diagnosed with major depressive disorder is brought to the emergency department after an attempted suicide by ingestion of rat poison. Which of the following receptor alteration will be most likely seen in this patient?
A. Increased 5-HT1A and 5-HT2A receptor expression in prefrontal cortex
B. Decrease in the α2-adrenergic receptor densities in hypothalamus
C. Decrease in the density of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors in the caudate nucleus
D. Increased density of μ-opioid receptors in frontal and temporal cortex
E. Decreased M1 and M4 receptor binding in anterior cingulate cortex
what is
A. Increased 5-HT1A and 5-HT2A receptor expression in prefrontal cortex
Explanation:
Patients with suicidal behavior have reduced serotonin activity in the central nervous system. 5-hydroxyindoleacetic acid (5-HIAA) is a metabolite of serotonin which is found in low levels in cerebrospinal fluid (CSF). Many studies have found low level of serotonin or 5-HIAA in the frontal cortex or brainstem in individuals who committed suicide. There are also significant changes in the serotonin receptors in these patients. There is an increase in the 5-HT1A and 5-HT2A serotonin receptors subtypes as well as increase in the protein expression of 5-HT2A receptor in the prefrontal cortex and hippocampus, which is a compensatory mechanism of the body to decreased serotonin activity of the neurons. Studies have shown patients who die by suicide have an increase in the β-adrenergic binding and an increase in the α2-adrenergic receptor densities and protein expression in the hypothalamus and frontal cortex. Patients with schizophrenia who commit suicide have an increase in the AMPA receptors specific for glutamate in the caudate nucleus. This is likely a compensatory mechanism for low level of glutamate. There is a decrease in the density of μ-opioid receptors in frontal and temporal cortex in patients with suicidal behaviors. There is significant increase in the binding of M1 and M4 muscarinic receptors in the anterior cingulate cortex in patients with suicidal behaviors.
A lesion of the left medial medulla will likely cause which one of the following results?
A. Impaired vibratory and position sensation on the right arm and leg
B. A left Horner syndrome
C. Impaired pain and temperature sensation in the right arm and leg
D. Impaired pain and temperature sensation on the left face
E. A left hemiplegia
what is Impaired vibratory and position sensation on the right arm and leg
The medial medullary syndrome often results from atherosclerotic occlusion of the vertebral artery, anterior spinal artery, or the lower segment of the basilar artery. Vertebrobasilar dissection, dolichoectasia of the vertebrobasilar system, embolus, and meningovascular syphilis are less common causes of medial medullary infarction. The anterior spinal artery supplies the paramedian region of the medulla oblongata, which includes the ipsilateral pyramid, medial leminiscus, and hypoglossal nerve and nucleus. Therefore, occlusion results in ipsilateral paresis, atrophy, and fibrillations of the tongue, contralateral hemiplegia sparing the face from pyramidal tract involvement, contralateral loss of position and vibratory sensation from involvement of the medial leminiscus, and occasionally upbeat nystagmus if the extent of the infarct extends dorsally towards the medial longitudinal fasciculus.
Which one of the following medications is FDA-approved to treat fibromyalgia?
A. Citalopram
B. Escitalopram
C. Fluoxetine
D. Gabapentin
E. Milnacipran
what is
E. Milnacipran
Explanation:
Selective serotonin reuptake inhibitors (SSRIs), e.g., fluoxetine (Prozac), citalopram (Celexa), escitalopram (Lexapro), fluvoxamine, paroxetine (Paxil), and sertraline (Zoloft), improve symptoms in fibromyalgia but have largely been replaced by dual serotonin/norepinephrine reuptake inhibitors (SNRIs), such as venlafaxine (Effexor), desvenlafaxine (Pristiq), milnacipran (Savella), which has recently been approved for fibromyalgia by the FDA, or duloxetine (Cymbalta), which has been shown to improve pain in fibromyalgia irrespective of comorbid depression. Of these, only milnacipran and duloxetine are currently approved by the FDA for pain in fibromyalgia. The anticonvulsant Pregabalin (Lyrica) is also FDA-approved for fibromyalgia. While discussing treatment options for fibromyalgia, it is also important to discuss non pharmacological strategies as well as diagnoses and treatment of comorbid depressive, anxiety symptoms.
Which one of the following tests represents the neurodiagnostic technique of choice to distinguish between a patient suspected to be suffering from frontotemporal neurocognitive disorder from one who may have Alzheimer's disease?
A. Electroencephalography
B. Magnetic resonance imaging (MRI)
C. Amyloid protein imaging
D. Computer tomography (CT)
E. Positron emission tomography (PET)
what is
The correct answer is:
E. Positron emission tomography (PET)
Explanation:
Positron emission tomography (PET) is an imaging technique that allows the examination of active biological processes, such as regional blood flow and glucose metabolism. Computer tomography (CT) scan may be normal in the early stages of the disease and MRI may reveal some focal atrophy of frontal and temporal lobes. However, PET studies reveal significant diminishment of glucose metabolism in these regions.The radioactive ligand used for PET imaging in dementia is fludeoxyglucose or 18F-FDG. Currently there is no evidence to suggest routine use of the modality to subtype dementia type.
A 58-year-old man with no past medical history and no history of EtOH use complains of a constant burning pain in his bilateral lower extremities. He has no family history of neuropathy. He has had a prior workup with another physician which included an unremarkable electromyography/nerve conduction velocity (EMG/NCV). You order a skin biopsy and expect to find:
A. Perivascular lymphocytic infiltrate
B. Neurolymphomatosis
C. Areas of pseudopalisading necrosis
D. Increased intraepidermal nerve fiber density
E. Decreased intraepidermal nerve fiber density
what is
E. Decreased intraepidermal nerve fiber density
Explanation:
This patient most likely has small fiber neuropathy which presents mostly with burning or tingling sensation in the lower limbs. This burning or tingling sensation is the most common and disabling symptom of small fiber neuropathy. Denervation or dysfunction of small nociceptive fibers leads to enhanced nerve excitability, causing neuropathic pain. Small fiber neuropathy is suspected when the patient presents with the above-mentioned symptoms and has no symptoms indicative of large fiber involvement, as is also indicated with no findings on the EMG. Damage to and marked reduction of individual intraepidermal nerve fibers is a pathological hallmark of small fiber neuropathy. The individual intraepidermal nerve fibers present in the biopsied skin are made visible through the use of immunohistochemical staining. This staining uses antibodies against protein gene product 9.5. This protein is expressed in neuronal cell bodies and axons. The severity of the denervation or reduction of the individual intraepidermal nerve fibers reflects the degree of functional impairment.