Neurofunctional Flashcards
Intraoperative test stimulation is being performed during a subthalamic nucleus deep brain stimulator placement. Stimulation at low voltages evokes dysconjugate gaze.
The lead position is likely too far in which direction?
a. Lateral
b. Medial
c. Anterior
d. Posterior
e. Superficial
b. Medial
Intraoperative test stimulation is routinely used during awake deep brain stimulation (DBS) surgery, both to test the clinical efficacy of the stimulation and to
assess for stimulation-induced side effects which may limit the efficacy of the technique. The subthalamic nucleus (STN) is located lateral and dorsal to the
oculomotor (III) fibers that emanate from the oculomotor nucleus. Stimulation-induced unilateral ocular deviation suggests recruitment of the oculomotor fibers
and that the active contact is too medial. Lateral placement can cause contralateral motor symptom due to corticospinal tract stimulation. Posterior stimulation
can cause sensory symptoms due to medial lemniscal stimulation.
What is the approximate seizure freedom rate in patients following non-lesional resective frontal lobe epilepsy surgery?
- 60-70%
- 20-30%
- 0-10%
- 40-50%
- 80-90%
- 40-50%
The correct answer is 40-50%. A number of clinical series have reported seizure freedom (Engel Class I) rates of 40-50% following frontal lobe epilepsy surgery.
A recent meta-analysis of 21 outcome studies reported an average rate across studies of 45% (Englot et al. 2012). This number is lower than that typically
observed for temporal lobe epilepsy, which is 60-70%. Negative prognostic factors for seizure freedom in frontal lobe epilepsy include normal imaging,
generalized scalp EEG abnormalities, and preoperative seizure frequency.
Which of the following structures is BEST described as lateral to the hippocampal complex (hippocampus, subiculum and parahippocampal gyrus)?
* Ambient cistern.
* Fusiform gyrus.
* Posterior cerebral artery.
* Brain stem.
* Oculomotor nerve.
- Fusiform gyrus.
The fusiform gyrus is lateral to the hippocampal complex. The fusiform gyrus has a functional role in color processing, face and body recognition, word and
number recognition, and within-category linguistic processing. The brain stem, oculomotor nerve, ambient cistern, and posterior cerebral artery are all in close
proximity and are medial to the hippocampal complex. The anatomy of these structures is best described in relationship to the brainstem, specifically the
midbrain. The oculomotor nerve exits the brainstem in the interpeduncular cistern and therefore lies anterior and medial to the hippocampal complex. The
posterior cerebral arteries arise from the terminal division of the basilar artery above the level of CNIII and can be visualized on the lateral surface of the midbrain
as it traverses towards and through the ambient cistern.
Which ONE of the following statements concerning essential tremor is TRUE?
* Thalamic stimulation of the ventralis intermedius nucleus for unilateral tremor is preferred over thalamotomy because the effects of the latter last for only several
years.
* A patient with tremor that begins after age 40 years should be tested for Wilson disease.
Primidone is probably somewhat superior to propanolol in treating essential tremor, but it causes more side effects in some patients and a significant number of
patients do not respond to either treatment.
* The presence of head tremor in addition to tremor of the extremities should make one question the diagnosis of essential tremor.
* The tremor of hyperthyroidism can be distinguished from essential tremor by recording devices that measure tremor frequency
Primidone is probably somewhat superior to propanolol in treating essential tremor, but it causes more side effects in some patients and a significant number of
patients do not respond to either treatment
Essential tremor is an action tremor at a frequency of 4 to 12 Hz. Involvement of the hands can be severely disabling as well as embarrassing. The head, trunk,
voice, and legs are sometimes also involved. Essential tremor becomes more manifest in the elderly patient. When evaluating a patient suspected of having
essential tremor, hyperthyroidism, caffeine, tobacco, and medications that might enhance physiological tremor, such as lithium, levothyroxine, valproate, and
prednisone, must be ruled out as the cause. When tremor occurs in a young patient, Wilson disease must be considered. Primidone and propanolol are both first
line drugs for essential tremor, with the former having somewhat more side effects initially but slightly more efficacy in the long term. Neurontin in high doses is
another drug that can be tried. The benzodiazepines are not as effective and cause more sedation. However, 25% to 55% of patients will have no response to
these drugs. Thalamic stimulation is the preferred method for medically unresponsive tremors that interfere with patient function. Thalamotomy is probably as
effective as stimulation in providing long lasting relief of tremor but is associated with more side effects, including decreased cognitive function and problems with
balance and speech. The preferred site is the ventralis nucleus intermedius of the thalamus
During deep brain stimulator implantation targeting the subthalamic nucleus, macrostimulation testing reveals good tremor control with low voltage stimulation but also
parasthesias that resolve rapidly and contralateral facial pulling and wrist flexion at low voltages. Similar findings are noted with stimulation at all contacts. What is the
most appropriate next step?
* Implantation should be aborted due to narrow therapeutic window.
* The lead should be moved laterally away from the red nucleus.
* The lead should be moved anteriorly due to the observation of transient parasthesias
* Secure the electrode in the current position due to an adequate therapeutic window.
* The lead should be moved medially away from the internal capsule.
The lead should be moved medially away from the internal capsule.
The lead should be moved medially away from the internal capsule due to observation of facial pulling and wrist flexion, indicating recruitment of the internal
capsule. Spread of current to the internal capsule resulting in contractions of the contralateral side of the face or extremity is one of the most common limitations
to DBS programming. Clear contractions are seen at amplitudes that are likely to be used for symptom suppression and these will likely persist during
postoperative programming. Contralateral facial pulling and wrist flexion at low voltages leave little room for postoperative programming and management. The
internal capsule is situated lateral and anterior to the subthalamic nucleus. Therefore, the lead should be moved medially or posteriorly to reduce spread of
current to the capsule and facilitate programming. Moving the lead anteriorly would move the lead closer to the internal capsule and likely result in internal
capsule recruitment at a lower threshold. While anterior tranposition of the lead is indicated for persistent parasthesias due to recruitment of the medial
lemniscus, transient parasthesias are common and are not an indication for lead movement.
You are placing a deep brain stimulator in the GPi for Parkinson’s disease. Your microelectrode has passed through the bottom of the GPi. What is the next structure to
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check for?
- Optic tract
- Substantia nigra reticulata
- Subthalamic nucleus
- VPL thalamus
- Globus pallidus externa
Optic tract
The sensorimotor area of the pallidum lies directly over the optic tract. Exit from the noisy GPi is marked by a transition through the lamina containing slow tonic
border cells followed by a silent area. Flashes of light directed at the patients eyes wil be picked up as a buzz in the microelectrode as one approaches the optic
tract in this region. Alternatively stimulation in this area can produce phosphenes in the patient’s contralateral visual field
Which of the following are the cardinal motor symptoms of Parkinson disease (PD) that are most amenable to treatment with deep brain stimulation (DBS)?
- Dyskinesia, bradykinesia and rigidity
- Bradykinesia, rigidity and tremor
- Dystonia, dyskinesia and tremor
- Freezing of gait, rigidity and tremor
- Dyskinesia, dystonia and freezing of gait
Bradykinesia, rigidity and tremor
The cardinal motor symptoms of Parkinson disease (PD) are bradykinesia, rigidity and tremor. These motor symptoms are most amenable to treatment using
deep brain stimulation (DBS). Other symptoms that can be seen in PD include freezing of gait, REM sleep disorders, autonomic disorders, and impulse control
disorders, among other motor and non-motor symptoms, yet these are typically less responsive to DBS therapy. Although dystonia and dyskinesia can be
improved with DBS therapy, these are not cardinal symptoms of PD. Dyskinesia is a side effect of levodopa therapy.
What is the FDA Human Device Exemption (HDE) approved target for deep brain stimulation for medically refractory obsessive compulsive disorder?
- Ventral capsule/ventral striatum
- Subthalamic nucleus Your Answer
- Anterior cingulate gyrus
- Subgenual cingulate gyrus
- Medial forebrain bundle
Ventral capsule/ventral striatum
DBS is approved under an FDA Humanitarian Device Exemption for obsessive compulsive disorder targeting the ventral anterior internal capsule and the ventral
striatum. This target was derived from earlier methods of anterior capsulotomies which were used for treatment of neuropsychiatric disease. The subgenual
cingulate gyrus (Area 25) is a putative target for neuromodulation for treatment-resistant depression. The anterior cingulate gyrus is a target for ablation for
medically refractory pain, depression, and obsessive compulsive disorder. Experience with neuromodulation at this target is limited. Subthalamic nucleus is a
common target for treatment of Parkinson’s disease and has been explored in the context of tremor and some psychiatric diseases, including OCD and addiction.
STN, however, is only FDA approved for the treatment of PD. The medial forebrain bundle has also been explored as a neuromodulation target due to its role in
the reward system, but it is not an FDA approved target.
A 42 year old male presents with a 5 year history of Parkinson disease (PD) with severe motor fluctuations. What would be his expected benefit from deep brain
stimulation (DBS) surgery?
* DBS wil provide improvement in freezing of gait, a motor symptom frequently associated with Parkinson disease.
* DBS wil result in reduction in progression of the natural history of Parkinson disease.
* DBS wil eliminate the need for Parkinson medications.
* DBS will provide improvement in motor symptoms comparable to the effects of Levadopa medication, with less motor fluctuations and without the medication-
induced dyskinesia
* DBS wil provide no benefit, because he has not had the disease long enough.
DBS will provide improvement in motor symptoms comparable to the effects of Levadopa medication, with less motor fluctuations and without the medication-
induced dyskinesia
In recent multicenter long-term studies, patients experience up to 4 hours more of motor symptom benefit with DBS, comparable to levodopa medication ON-time
effects, but without dyskinesias. DBS for PD is considered an adjunctive treatment to medications. Based on randomized clinical trials, medications can be
reduced up to 20-40% over time, but in most instances, they are not eliminated completely. However, the frequency with which they need to be taken is reduced,
reducing the on/off motor fluctuations commonly experienced. Deep brain stimulation only improves levodopa responsive symptoms including bradykinesia,
rigidity, and tremor. Freezing of gait on levodopa therapy, postural instability, and non-motor symptoms of PD are unlikely improve with DBS, and may even
worsen following surgery. DBS has NOT been shown to modulate the natural history of PD. Duration of disease is not a primary criteria for surgical selection,
although symptoms should persist long enough to be confident of the diagnosis of PD.
When considering targets for deep brain stimulation for a patient with advanced Parkinson’s disease, what is true about the expected benefits of stimulation of the
subthalamic nucleus (STN) over the globus pallidus internus (GPi)?
* Superior motor outcomes in patients under age 50.
* Greater reduction in overall disability score.
* Fewer neurocognitive side effects.
* Greater medication reduction.
* Greater longevity of therapy.
- Greater medication reduction.
In the management of patients with Parkinson’s disease, deep brain stimulation targeting the subthalamic nucleus is associated with greater medication reduction
than when stimulation the GPi. This is a common and repeated observation across both institutional observational studies as well as randomized controlled trials.
In the VA cooperative study, PD patients who underwent STN DBS had on average a 30-40% reduction in their dopamine equivalent requirements while patients
who underwent GPi DBS had on average only a 15-20% reduction in their dopamine requirements (p=0.02). While STN DBS is associated with decreased
medication requirements, it is also usually associated with an increased risk of neurocognitive sequelae, such as greater impairment in visuomotor processing
and depression. With respect to motor control, randomized controlled trials suggest equal motor efficacy and equal impact on disability scores. There is no
definitive objective data comparing longevity of therapy. Likewise, there is no data supporting differences in efficacy in young vs. older patients.
After invasive grid monitoring and mapping of eloquent cortex, surgical resection is recommended for a 19-year-old man with drug-resistant epilepsy. The patient’s
seizures involve speech arrest with tonic posturing of the upper extremities in a “fencing posture”. Where is the likely seizure focus?
* Primary sensory cortex
* Supplementary motor area
* Primary motor cortex
* Mesial temporal lobe.
* Lateral temporal lobe
Supplementary motor area
Tonic posturing of the limbs (often with ipsilateral elbow extension and contralateral elbow flexion and shoulder abduction in a “fencing posture”) is common in
seizures originating in the supplementary motor area (SMA). Motor cortex seizures often spread in a “Jacksonian march” along the somatotopic organization of
the homunculus. Temporal lobe seizures are often complex-partial with impaired consciousness and automatisms involving the hands (fidgeting, picking) or
mouth (lip smacking, chewing), while sensory cortex seizures typically involve contralateral paresthesias with preserved consciousness.
Which anti-epileptic agents would be BEST to use in a patient receiving multiple other medications extensively metabolized by the liver?
* Levetiracetam (Keppra)
* Phenytoin (Dilantin)
* Carbamazepine (Tegretol)
* Phenobarbital (Luminal)
* Oxcarbazepine (Trileptal)
- Levetiracetam (Keppra)
Induction of hepatic enzymes can have pharmacologically significant effects on the metabolism of drugs which are eliminated by the liver. In particular, the
plasma levels of an entire new class of anti-cancer drugs, synthesized small molecule signal transduction inhibitors, are dramatically affected by hepatic enzyme
induction. Of all of the currently available anti-epileptic drugs, phenytoin, carbamazepine (and the related oxcarbazemine) and phenobarbital are the most potent
inducers of hepatic enzymes. Levetiracetam does not significantly induce hepatic enzymes and may be a favorable alternative in patients who are receiving other
medications which are extensively metabolized by the liver.
A craniotomy using frameless stereotactic guidance is planned. After the surgeon registers the patient and image, the fiducial reference frame moves in relation to the
patient. Which of the following is the best option before proceeding with the operation?
* Return the reference frame to its previous position
* Re-register
* Touch a skull reference point
* Use a software correction algorithm
* Ignore the shift if minor
- Re-register
Maintenance of registration in infrared-based frameless stereotaxy relies on use of a fiducial reference frame whose spatial relationship to the head remains
constant. Without this, any change in relative position of the patient’s head to the cameras (e.g., by table movements or casual bumps of the camera stand) wil
render the registration inaccurate. No software algorithms or other shortcuts can correct this problem. If it occurs, the surgeon must decide whether frameless
stereotaxy is still necessary. If so, repeat registration wil be necessary. Reliance on frankly inaccurate surgical navigation can result in surgical catastrophes.
Stimulation in what peri-Sylvian region would most likely cause speech arrest during awake speech mapping?
* Pars triangularis
* Pars opercularis
* Gyrus supramarginalis
* Pars orbitalis
* Gyrus angularis
- Pars opercularis
The correct answer is pars opercularis. When performing surgery near the perisylvian cortex in the dominant hemisphere, the localization of language is one of
the most important factors in planning a cortical trajectory or resection and, consequently, minimizing the risk of a postoperative language deficit. For most
patients Broca’s area is adjacent to, and distributed evenly around, the inferior precentral sulcus, or pars opercularis. In others, Broca’s area is adjacent to the
accessory sulcus that lies immediately posterior to the inferior precentral sulcus. Therefore, awake speech mapping has to be performed to minimize the risk of
new neurological deficits as wel as to push to the limits the extent of resection of the tumor.
What is a known possible side effect of corpus callosotomy for epilepsy?
* Disconnection syndrome
* Superficial cerebral hemosiderosis
* Hemibalismus
* Hemiplegia
* Gerstmann syndrome
Disconnection syndrome
The correct answer is disconnection syndrome, also known as callosal or split brain syndrome. This consists of the inability to name objects
although one is capable of recognizing them. Superficial cerebral hemosiderosis, which is a delayed symptom complex of sensorineural
hearing loss, ataxia, dementia, pyramidal signs, and possibly anosmia, is associated with anatomic hemispherectomies. Gerstmann
syndrome results from a more refined lesion or injury to the dominant (typically left) parietal cortex and results in dysgraphia, dyscalculia,
finger agnosia, and right-left disorientation. Hemibalismus is a syndrome of wild flinging movements of the contralateral side of the body to an
injured subthalamic nucleus.
An eight-year old male of Ashkenazi Jewish descent presents with generalized dystonia, refractory to al medications. A similar condition has been noted in a number of
his first-degree relatives. Which bilateral procedure is the BEST option for surgical treatment of this condition?
* Thalamotomy
* Subthalamic deep brain stimulation
* Pallidotomy
* Pallidal deep brain stimulation
* Thalamic deep brain stimulation
Pallidal deep brain stimulation
The patient is likely to have an inherited idiopathic generalized dystonia, most commonly due to a mutation in DYT1. Very few medications are efficacious in this
disorder, while deep brain stimulation of the globus pallidus internus has been shown to have dramatic clinical efficacy. Pallidal stimulation has been found to be
more effective in the pediatric population than the adult population. The efficacy of stimulation improves with time. Other targets have not been shown to be as
effective. Bilateral pallidal lesions, in addition to less satisfactory therapeutic effect, have been associated in various patient populations with a number of serious
functional side effects. STN DBS is often used in Parkinson Disease, and thalamic (Vim nucleus) DBS is effective for Essential Tremor.
A 65-year-old male presents with resting tremor, rigidity, postural instability, and bradykinesia. Which of the following symptoms is most likely to also be present?
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* Diarrhea
* Hyposmia
* Diabetes
* Dry mouth
* Hypertension
Hyposmia
Patient has the cardinal features of Parkinson’s disease. Common non-motor symptoms of PD include neuropsychiatric problems and mood disorders; sleep
disturbances, constipation and bladder problems, orthostatic hypotension, excessive salivation, and loss of sense of smell and taste. Other non-motor symptoms
include medication side effects with levodopa therapy, including impulsive behavior and hallucinations.
A 60-year-old generally healthy man with Parkinson disease (PD) is considering undergoing deep brain stimulation electrode implantation. He was diagnosed with PD 8
years ago and responded extremely well to levodopa therapy initially. Last year, he began to develop levodopa-related dyskinesias. Which of the following factors is
most predictive of his response to deep brain stimulation?
* Levodopa responsiveness
* Development of levodopa-induced dyskinesias
* Duration of disease
* Age
* Lack of medical comorbidities
Levodopa responsiveness
Response to levodopa is accepted as the best predictor of DBS success. Age and medical comorbidities may serve as relative contraindications to surgery in
patients older than 75 years of age or comorbidities such as unstable heart disease, severe cerebrovascular disease or other serious neurological or cardiac
comorbidities, but do not necessarily preclude placement. Duration of disease and dyskinesias have not been associated with DBS outcomes although DBS
performed after a mean of 4 years and within 3 years of dyskinesia development has been shown to be superior to medical therapy.
In the Hassler terminology, the ventrolateral thalamus is subdivided into three regions, including which of the following:
* Ventraloralis anterior (VOA), ventral intermiate (VIM), and ventral caudalis (VC)
* Ventral lateral (VL), ventral intermediate (VIM), and ventral posterior lateral (VPL)
* Ventral oralis anterior (VOA), ventral oralis posterior (VOP), and ventral caudalis
* (VC) Ventral oralis anterior (VOA), ventral oralis posterior (VOP), and ventral intermediate (VIM)
* Ventral oralis posterior (VOP), ventral intermediate (VIM), and ventral caudalis (VC)
Ventral oralis posterior (VOP), ventral intermediate (VIM), and ventral caudalis (VC)
The correct answer is ventral oralis anterior (VOA), ventral oralis posterior (VOP), and ventral intermediate (VIM). The Hassler classification subdivides the
ventrolateral nucleus of the thalamus into three discrete regions: VOA, VOP, and VIM. These are arranged, respectively, anterior to posterior. VIM and VOP
receive cerebellar innervation predominantly and are the primary target for tremor suppression. VOA receives afferents from the globus pallidus pars internus
(GPi) and has been targeted for the treatment of medically refractory dystonia, although targeting the GPi itself seems to generate superior results. The ventral
caudalis (VC) nucleus of the thalamus is also part of the Hassler classification, but it describes the region posterior to the three ventrolateral subdivisions, which
receives sensory input into the thalamus. The VC has been used as a target to treat central neuropathic pain. The Walker nomenclature is another
classification scheme, in which Hassler’s VOA and VOP is called the ventral lateral (VL) nucleus, Hassler’s VIM is still called the VIM, and Hassler’s VC is
called the ventral posterior lateral (VPL) nucleus. These are depicted in the figure below.
A patient is undergoing DBS lead placement in the subthalamic nucleus for Parkinson disease. During intraoperative testing the patient has good relief of symptoms but
also notes facial pulling and transient paresthesias. Different monopolar and bipolar options produce the same result. Which of the following is the best option?
* Move the lead medially
* Abort implantation on this side andmove on to DBS implantation on the left sideLeave the DBS in its current location
* Move the lead laterall]Advance the lead deeper
- **Move the lead medially **
- Abort implantation on this side and move on to DBS implantation on the left side.
- Leave the DBS in its current location
- Move the lead laterally
- Advance the lead deeper
Spread of current to the internal capsule resulting in contractions of the contralateral side of the face or extremity is one of the most common limitations to DBS
programming. Clear contractions are seen at the same amplitudes that will be used for symptom suppression and these will likely persist during postoperative
programming. The internal capsule is situated lateral and anterior to the subthalamic nucleus. Contractions observed during macrostimulation usually indicate
lateral placement of the lead and/or anterior placement of the lead. In this example, transient paresthesias indicate that the lead is more posteriorly placed in the
nucleus and not too far anterior. Moving the lead to a more medial location will likely reduce spread of current to the capsule and facilitate programming
