1. (A): Because of the orientation of the dipole deep inside the longitudinal fissure (for the lower extremity), the cortical potential is better recorded over the ipsilateral centroparietal region. This is referred to as the paradoxical localization. Conversely, in the case of the upper extremity, recording is made on the contralateral side. (Daube 2002, p. 189; Ebersole and Pedley 2003, p. 937)

2. (D): All of the mentioned parameters are considered to be alarming changes during SSEP monitoring. When the potentials are lost, technical causes should be ruled out first before calling it abnormal. (Møller 2006, pp. 136-137)

3. (B): Contrary to peripheral nerve stimulation, the active electrode in transcranial motor stimulation is the anode. Electrical stimulation is favored over magnetic stimulation when performing such studies because of more robust response and better reproducibility. (Møller 2006, pp. 180-181)

4. (A): Anesthesia levels may significantly alter evoked potential latencies and amplitude. Similar to hypotension and hypothermia, anesthesia-induced changes are systemic, affecting potentials of all limbs equally. Cortical potentials are the most sensitive to these changes while peripheral and cervical potentials are most resistant. (Ebersole and Pedley 2003, p. 938; Møller 2006, p. 137)

5. (C): The normal cerebral blood flow is 50 cc/100 g/minute. EEG may show signs of slow activity when the blood flow reaches 15 to 25 cc/100 g/minute. EEG attenuation typically occurs when blood flow reaches 12 cc/100 g/minute. (Ebersole and Pedley 2003, pp. 949-950)

6. (B): Loss of higher frequency waveforms is the first alarming sign of brain ischemia during carotid endarterectomy followed by voltage or amplitude asymmetry. Care must be taken to differentiate loss of higher frequency from hypocarbia, hypotension, hypothermia, and anesthesia. Of note, some inhaled anesthetic and intravenous agents such as benzodiazepines or barbiturates increase high frequency waveforms. (Daube 2002, pp. 528-529)

7. (C): Needle electrodes are the preferred types of electrodes used in neurophysiologic intraoperative studies. Platinum or disposable needle electrodes are preferred because they provide better stability when patient positions and manipulation is modified throughout the surgery. Taped needle electrodes are less likely to be dislodged or removed accidentally during the long surgical procedures. The disadvantages of such electrodes are the relatively higher degree of invasiveness as well as their higher impedance. (Møller 2006, p. 41)

8. (D): Hypothermia causes prolongation of peripheral, cervical, and cortical SSEP latencies. Inhalational agents and hypotension causes prolongation of cortical SSEP latencies. Peripheral and cervical SSEPs are more resistant to changes induced by anesthesia or hypotension. (Møller 2006, p. 137; Ebersole and Pedley 2003, pp. 837-938)

9. (B): During carotid endarterectomy, the risk of cerebral ischemia maybe prevented with the use of shunts to bypass the area of clamping. Routine placement of shunts carries a ten times greater risk for embolic strokes than that with the selective use of shunts. This explains the great usefulness of intraoperative EEG to prompt the use of shunts only when cerebral ischemia is detected. (Daube 2002, p. 137)

10. (B): Intraoperative monitoring of the facial nerve function is regarded as a valuable adjunct to vestibular schwannoma resections due to its anatomical proximity to the eighth cranial nerve. It is often performed along with intraoperative BAEP monitoring. The orbicularis oris is an easily accessible muscle innervated by the buccal branch of the facial nerve. (Møller 2006, pp. 198-199)

11. (B): The response from descending corticospinal tracts is recorded from the spinal cord using epidural electrodes. Transcortical stimulation of the motor pathways generates D and I waves. The D wave is assumed to be elicited by direct stimulation of the dorsal corticospinal tracts and consists of negative peaks. Similar to the I wave, it is not influenced by the use of muscle relaxants. (Møller 2006, pp. 183-184)

12. (D): EMG potentials from extraocular muscles are typically monitored during skull base surgeries such as carvenous sinus tumor resections. Needle electrodes are placed directly into the muscles or near the extraocular muscles. EMG activity from the lateral rectus (CN VI), inferior rectus (CN III), and superior oblique (CN IV) muscles is most commonly recorded. The reference electrode is placed on the forehead, contralateral to the monitored eye to minimize interference from the extraocular muscle contraction. (Møller 2006, pp. 206-208)

13. (D): During BAEP monitoring, several factors may cause prolongation of waveform latencies and attenuation of waveform amplitude. Of these are cerebellum retraction, hypothermia, or hyperthermia. These changes are transient if the cause is reversed. (Møller 2006, pp. 105-108)