CNIM Practice Exam 1 with complete solutions

During a median nerve preoperative study, a patient has discomfort at the wrist. Stimulation electrodes are 10 mm gold disk, stimulus intensity is 20 mA, and stimulus duration is 100 μsec. Which of the following would most likely reduce the patient's discomfort while maintaining adequate stimulation? - Answer- Decrease number of repetitions What is not an advantage of epidural recordings? - Answer- Absence of significant artifact The stimulation rate is determined by the - Answer- analysis time Somatosensory evoked potentials are less reliable in patients with ? - Answer- Neuromuscular disease When placing PTN stimulator you should not - Answer- Secure the tape and bands around the whole ankle A differential amplifier with a Gain of 1,000,000 has a 0.2 μV signal at its positive input and a 0.8 μV signal at its negative input. The output will be: - Answer- A downward peak of 0.6V The lumbar potential is generated from - Answer- Post-synaptic responses The P31 response to posterior tibial nerve stimulation - Answer- Is recordable over a generalized region of scalp Which of the following has the greatest effect on SEP monitoring? - Answer- Sevoflurane A shocking sensation that occurs throughout the body during neck flexion is called - Answer- L'Hermittes sign Lowering the SSEP hicut filter from 500 Hz to 200 Hz may cause the cortical peaks to: - Answer- Appear longer in latency How many waves of a 60 Hz signal should you see in a 250 mS sweep? - Answer- 15 Activation of an action potential of a neuron will depend on: - Answer- Its membrane potential based on the spatiotemporal summation of its excitatory and inhibitory inputs From left to right pre-auricular points is measured 30 cm. The C3 electrode is located: - Answer- 9 cm medial to the left pre-auricular point The most frequent source of patient infection in the operating room derives from: - Answer- The patient's own endogenous flora What is the maximum time in which to expect EEG changes following cross clamping of the carotid? - Answer- Two minutes Cranial nerve IV can be monitored using electrodes inserted into the - Answer- Superior oblique According to the nurses guidelines how far do you need to be from the sterile field? - Answer- 18 inches When no phase reversal is present in an anterior-posterior cortical grid recording: - Answer- The maximum amplitude response is closest to the central sulcus EEG will most likely disappear at what body temperature - Answer- 16 degrees C Epileptiform discharges can be localized by: - Answer- A phase reversal between two channels Why is platinum used in epidural recordings - Answer- Other metals become toxic when current is applied to them due to the ionic What will most likely effect SSEPs? - Answer- Spinal cord tumor Excessive cerumen may cause - Answer- Absence of the BAER Which of the following can increase SEP amplitude? - Answer- Etomidate Which montage would you use to confirm a change in the Cz'-Fz cortical response to PTN stimulation? - Answer- Cpc-Cpi CNS depressants cause: - Answer- Minimal effects in ABRs After-discharges occur after what? - Answer- Direct cortical stimulation An ABR has a normal wave one and then delayed wave I-V on one side. What type of surgery is this most consistent with? - Answer- CPA Tumor An optimal repetition rate for BAEP's is - Answer- 31Hz The input impedance of a differential amplifier should be: - Answer- At least 100 Megaohms Lower motor neurons primarily exit the spinal cord through: - Answer- Ventral nerve roots Lack of after-discharges indicates: - Answer- The stimulus is likely below the threshold of seizure activation There were epidural recordings to PTN stim from T5 and from C7. The T5 had a stable response throughout the tumor surgery, while the C7 had no response and then a great one after the tumor removal. Where was the tumor? - Answer- Rostral to T6 and caudal to C7 What is the advantage to using an insulated bipolar electrode for intracranial facial nerve stimulation? - Answer- Prevent current shunting to other cranial nerves What is the maximum allowable leakage current from the isolated amplifier inputs through the patient leads? - Answer- 10 μA When you stimulate PTN where do you want to record your TO4? - Answer- Abductor Hallucis Brevis The most appropriate ABR interstimulus interval is: - Answer- 20mS Which of the following is NOT a safety concern regarding the use of TcMEPs? - Answer- Patient history of cerebral palsy What is the minimum required vertical resolution of an evoked potential system? - Answer- 8 bits Which of the following is most affected by halogenated agents? - Answer- Posterior tibial cortical potential A 10-bit A/D Converter has how many discrete voltage values in its range? - Answer- 1024 If you cannot replace an electrode that has come out during surgery you: - Answer- Use a duplicate The C8 nerve root exits the spinal cord: - Answer- Above the T1 vertebrae When an electrode falls on the floor you: - Answer- You immediately pick it up and dispose of it in a sharps container A 60 Hz artifact would most likely be caused by - Answer- Infusion pump Midazolam is what type of drug? - Answer- Benzodiazepine If you get artifact in you subcortical channel you: - Answer- Use a spare CS5 electrode Where is the ABR wave V generated? - Answer- Midbrain How should needle electrodes be discarded? - Answer- Only is a red puncture-proof sharps container What is the most common reason for loss of BAEPs during retromastoid microvascular decompression? - Answer- Compromise vascular supply