- Email: [email protected]
Usefulness of somatosensory and motor evoked potentials for lesion localization
Clinical Neurology and Neurosurgery 115 (2013) 1917–1925
Contents lists available at ScienceDirect
Clinical Neurology and Neurosurgery journal homepage: www.elsevier.com/locate/clineuro
Letters to the Editor Isolated brainstem cysticercosis Sir, The recent article on isolated brainstem cysticercosis is very interesting [1]. Del Brutto et al. concluded that this condition can present as “space-occupying lesion” and also mentioned that “The prognosis is benign provided the patients receive prompt therapy [1].” Some additional concerns should be mentioned. First, the differential diagnosis from other space occupying lesions is needed. However, the diagnosis by neuroimaging might be very difficult. Chang et al. concluded that “The clinical and radiographic features of neurocysticercosis are highly variable [2].” The final diagnosis has to be based on “surgical and histopathological findings [2].” Furthermore, the concurrent neurocysticercosis and tumor can be seen and this should not be missed [3]. Focusing on the course of disease, it sometimes can be fatal. Basilar infestation can induce brain herniation and can result in death [4]. References [1] Del Brutto OH, Del Brutto VJ. Isolated brainstem cysticercosis: review. Clinical Neurology and Neurosurgery 2013;(January), a http://dx.doi.org/10.1016/j.clineuro.2012.12.026 [pii: S0303-8467(13)00003-6. Epub ahead of print]. [2] Chang JH, Chang JW, Park YG, Kim TS. Cysticercosis of cerebellopontine cistern: differential diagnosis using MRI. Acta Neurochirurgica (Wien) 2004;146(April (4)):325–8. [3] Vij M, Jaiswal S, Jaiswal AK, Behari S. Coexisting intramedullary schwannoma with intramedullary cysticercus: report of an unusual collision. Indian Journal of Pathology & Microbiology 2011;54(October–December 4):866–7. [4] McCormick GF. Cysticercosis—review of 230 patients. Bulletin of Clinical Neurosciences 1985;50:76–101.
Viroj Wiwanitkit a,b,c,∗ Hainan Medical University, China b Faculty of Medicine, University of Nis, Serbia c Joseph Ayobabalola University, Nigeria a
∗ Correspondence
address: Wiwanitkit House, Bangkhae, Bangkok 10160, Thailand. Tel.: +662 2564136. E-mail address: [email protected] 30 January 2013 Available online 26 February 2013
http://dx.doi.org/10.1016/j.clineuro.2013.02.003
Usefulness of somatosensory and motor evoked potentials for lesion localization Dear Editor, We have read with great interest the recent study published by Hellmann et al. [1]. This study included 12 patients who had
0303-8467/$ – see front matter © 2013 Elsevier B.V. All rights reserved.
paraparesis and thoracic sensory loss with normal thoracic magnetic resonance imaging (MRI). The authors concluded that for such patients, MRI of the cervical spinal cord and, if needed, of the brain should be performed. In clinical practice, a thoracic lesion is suspected if the 1st motor neuron of the lower extremities is involved, the upper extremities show no abnormalities, and physical findings are present. When ipsilateral upper extremities are involved, lesions are suspected to be present in the brain and cervical region. However, sometimes, lesions in regions different from those suspected are detected. In this study, the authors stressed on this crucial topic and stated that cervical imaging and, if necessary, brain imaging would be important for patients with thoracic sensory loss but normal thoracic MRI findings. In addition to this suggestion by the authors, we think that somatosensory evoked potential (SEP) measurements would be beneficial for their patients with marked sensory complaints and motor evoked potential (MEP) measurements would benefit their patients with marked weakness. SEP can be used for monitoring transmissions in the contralateral side of the primary somatosensory cortex that pass through the thick myelinated fibers to the spinal cord and then travel along the posterior cord fibers and medial lemniscus pathway. The median nerve is usually used to stimulate the upper extremity. Recordings from upper extremities can be obtained by placing the electrodes on the ipsilateral Erb’s point, on the midpoint of cervical-5 (using glottis as reference), and according to the 10–20 EEG system, on to the C3 and C4 regions where they would be contralateral to the stimulation point. The tibial nerve is usually used to stimulate the lower limbs. Recordings from the lower limbs are obtained by placing the electrodes on the midpoint of thoracal 12, the midpoint of cervical-5, and the Cz . Elongation of transmission time between the mentioned points of electrode placement or a lack of response might indicate the localization of the lesion [2]. In some cases, it would be useful to compare SEPs obtained after stimulation of the tibial nerve with those obtained after stimulation of the peroneal nerve, sural nerve, ulnar nerve, and median nerve because the volleys along the spinal cord run on different pathways [3]. However, practitioners must remember that SEP recording from cervical-5 may be absent even in normal subjects following stimulation of a mixed nerve of a lower limb. MEPs recordings are usually obtained by placing the electrodes on the abductor pollicis brevis and abductor hallucis muscles. Importantly, practitioners should keep in mind that different points can be stimulated with MEP and recordings from different points can be obtained using the myotomal chart. MEP recordings from muscles with evident loss of strength can be useful [4]. We think that SEP and MEP can indicate the location of a lesion more precisely, and deciding to perform imaging on the basis of SEP and MEP results would help save time and resources. Furthermore, SEP and MEP can be monitored after completion of treatment in order to determine if the electrophysiological evaluation was beneficial or not.
1918
Letters to the Editor / Clinical Neurology and Neurosurgery 115 (2013) 1917–1925
Nitin K. Sethi ∗ Department of Neurology, New York-Presbyterian Hospital, Weill Cornell Medical Center, New York, USA
References [1] Hellmann MA, Djaldetti R, Luckman J, Dabby R. Thoracic sensory level as a false localizing sign in cervical spinal cord and brain lesions. Clinical Neurology and Neurosurgery 2013;115(January (1)):54–6. [2] Starr A. Sensory evoked potentials in clinical disorders of the nervous system. Annual Review of Neuroscience 1978;1:103–27. Review. [3] Rossini PM, Gigli GL, Zarola F, Marciani MG, Caramia M, Bernardi G. On the spinal pathways mediating scalp-SEPs to upper and lower limb nerve stimulation: case report and discussion. Acta Neurologica Scandinavica 1986;74(September (3)):230–4. [4] Schwartz DM, Sestokas AK, Dormans JP, Vaccaro AR, Hilibrand AS, Flynn JM, et al. Transcranial electric motor evoked potential monitoring during spine surgery: is it safe? Spine (Phila Pa 1976) 2011;36(June (13)):1046–9.
Hakan Akgün ∗ Etimesgut Military Hospital, Department of Neurology, Ankara, Turkey Mehmet Yücel Kasımpas¸a Military Hospital, Department of Neurology, Istanbul, Turkey O˘guzhan Öz S¸eref Demirkaya Gülhane Military Medical Academy, Department of Neurology, Ankara, Turkey
∗ Correspondence address: Comprehensive Epilepsy Center, New York-Presbyterian Hospital, Weill Cornell Medical Center, 525 East, 68th Street, New York, NY 10065, USA. Tel.: +1 212 746 2346; fax: +1 212 746 8845. E-mail address: [email protected]
23 February 2013 Available online 18 March 2013 http://dx.doi.org/10.1016/j.clineuro.2013.02.022
Scrotal swelling due to migration of the abdominal catheter of a cyst-peritoneal shunt Keywords: Scrotal Swelling Cyst-peritoneal shunt
Dear Editor,
∗ Corresponding
author. Tel.: +90 312 2491011; fax: +90 312 3044475. E-mail addresses: [email protected], [email protected] (H. Akgün) 13 January 2013 Available online 5 March 2013
http://dx.doi.org/10.1016/j.clineuro.2013.02.011
Electrophysiological mapping for eloquent cortex during awake craniotomy
A 30-year-old man presented with a history of left scrotum swelling for over a week without fever. There was no previous history of epididymitis or orchitis and physical examination revealed no palpable inguinal hernia. His past medical history revealed a cystic-peritoneal (C-P) shunt placement 6 months ago because of a large arachnoid cyst of the left middle cranial fossa [Fig. 1]. A shunt series was performed and abdominal X-ray demonstrated the caudal end of the shunt to project over the left scrotum [Fig. 2], suggesting shunt migration. The patient was taken up for exploratory laparotomy and the peritoneal catheter was repositioned. Prophylactic obliteration of the patent processus vaginalis was performed to prevent recurrence. The patient was regularly followed up at
Keywords: Cortical mapping Awake craniotomy
Dear Editor, I read with interest Chacko et al. [1] experience on awake craniotomy with electrophysiological mapping for resection of eloquent area tumors. Ideally the lowest current which elicits a positive response indicates presence of eloquent cortex. The threshold for eliciting a response depends upon the proximity of the cortical stimulator to the eloquent cortex and also the intensity of the stimulating current. Set the stimulating current too high and you risk a false positive result due to spread of current to adjacent eloquent cortex thus potentially limiting the extent of the surgery. Set the current too low and you risk a false negative response with resultant inadvertent damage to eloquent brain tissue. Will the authors please comment on their stimulation techniques and experience with the same. Did they find that one approach fits all or did they modify their technique based on type of eloquent cortex and preoperative imaging showing extensive distortion of brain architecture and mass effect?
Reference [1] Chacko AG, Thomas SG, Babu KS, Daniel RT, Chacko G, Prabhu K, et al. Awake craniotomy and electrophysiological mapping for eloquent area tumours. Clinical Neurology and Neurosurgery 2013;115:329–34.
Fig. 1. CT scan demonstrating shunt catheter placement in a left middle cranial fossa arachnoid cyst.
Contents lists available at ScienceDirect
Clinical Neurology and Neurosurgery journal homepage: www.elsevier.com/locate/clineuro
Letters to the Editor Isolated brainstem cysticercosis Sir, The recent article on isolated brainstem cysticercosis is very interesting [1]. Del Brutto et al. concluded that this condition can present as “space-occupying lesion” and also mentioned that “The prognosis is benign provided the patients receive prompt therapy [1].” Some additional concerns should be mentioned. First, the differential diagnosis from other space occupying lesions is needed. However, the diagnosis by neuroimaging might be very difficult. Chang et al. concluded that “The clinical and radiographic features of neurocysticercosis are highly variable [2].” The final diagnosis has to be based on “surgical and histopathological findings [2].” Furthermore, the concurrent neurocysticercosis and tumor can be seen and this should not be missed [3]. Focusing on the course of disease, it sometimes can be fatal. Basilar infestation can induce brain herniation and can result in death [4]. References [1] Del Brutto OH, Del Brutto VJ. Isolated brainstem cysticercosis: review. Clinical Neurology and Neurosurgery 2013;(January), a http://dx.doi.org/10.1016/j.clineuro.2012.12.026 [pii: S0303-8467(13)00003-6. Epub ahead of print]. [2] Chang JH, Chang JW, Park YG, Kim TS. Cysticercosis of cerebellopontine cistern: differential diagnosis using MRI. Acta Neurochirurgica (Wien) 2004;146(April (4)):325–8. [3] Vij M, Jaiswal S, Jaiswal AK, Behari S. Coexisting intramedullary schwannoma with intramedullary cysticercus: report of an unusual collision. Indian Journal of Pathology & Microbiology 2011;54(October–December 4):866–7. [4] McCormick GF. Cysticercosis—review of 230 patients. Bulletin of Clinical Neurosciences 1985;50:76–101.
Viroj Wiwanitkit a,b,c,∗ Hainan Medical University, China b Faculty of Medicine, University of Nis, Serbia c Joseph Ayobabalola University, Nigeria a
∗ Correspondence
address: Wiwanitkit House, Bangkhae, Bangkok 10160, Thailand. Tel.: +662 2564136. E-mail address: [email protected] 30 January 2013 Available online 26 February 2013
http://dx.doi.org/10.1016/j.clineuro.2013.02.003
Usefulness of somatosensory and motor evoked potentials for lesion localization Dear Editor, We have read with great interest the recent study published by Hellmann et al. [1]. This study included 12 patients who had
0303-8467/$ – see front matter © 2013 Elsevier B.V. All rights reserved.
paraparesis and thoracic sensory loss with normal thoracic magnetic resonance imaging (MRI). The authors concluded that for such patients, MRI of the cervical spinal cord and, if needed, of the brain should be performed. In clinical practice, a thoracic lesion is suspected if the 1st motor neuron of the lower extremities is involved, the upper extremities show no abnormalities, and physical findings are present. When ipsilateral upper extremities are involved, lesions are suspected to be present in the brain and cervical region. However, sometimes, lesions in regions different from those suspected are detected. In this study, the authors stressed on this crucial topic and stated that cervical imaging and, if necessary, brain imaging would be important for patients with thoracic sensory loss but normal thoracic MRI findings. In addition to this suggestion by the authors, we think that somatosensory evoked potential (SEP) measurements would be beneficial for their patients with marked sensory complaints and motor evoked potential (MEP) measurements would benefit their patients with marked weakness. SEP can be used for monitoring transmissions in the contralateral side of the primary somatosensory cortex that pass through the thick myelinated fibers to the spinal cord and then travel along the posterior cord fibers and medial lemniscus pathway. The median nerve is usually used to stimulate the upper extremity. Recordings from upper extremities can be obtained by placing the electrodes on the ipsilateral Erb’s point, on the midpoint of cervical-5 (using glottis as reference), and according to the 10–20 EEG system, on to the C3 and C4 regions where they would be contralateral to the stimulation point. The tibial nerve is usually used to stimulate the lower limbs. Recordings from the lower limbs are obtained by placing the electrodes on the midpoint of thoracal 12, the midpoint of cervical-5, and the Cz . Elongation of transmission time between the mentioned points of electrode placement or a lack of response might indicate the localization of the lesion [2]. In some cases, it would be useful to compare SEPs obtained after stimulation of the tibial nerve with those obtained after stimulation of the peroneal nerve, sural nerve, ulnar nerve, and median nerve because the volleys along the spinal cord run on different pathways [3]. However, practitioners must remember that SEP recording from cervical-5 may be absent even in normal subjects following stimulation of a mixed nerve of a lower limb. MEPs recordings are usually obtained by placing the electrodes on the abductor pollicis brevis and abductor hallucis muscles. Importantly, practitioners should keep in mind that different points can be stimulated with MEP and recordings from different points can be obtained using the myotomal chart. MEP recordings from muscles with evident loss of strength can be useful [4]. We think that SEP and MEP can indicate the location of a lesion more precisely, and deciding to perform imaging on the basis of SEP and MEP results would help save time and resources. Furthermore, SEP and MEP can be monitored after completion of treatment in order to determine if the electrophysiological evaluation was beneficial or not.
1918
Letters to the Editor / Clinical Neurology and Neurosurgery 115 (2013) 1917–1925
Nitin K. Sethi ∗ Department of Neurology, New York-Presbyterian Hospital, Weill Cornell Medical Center, New York, USA
References [1] Hellmann MA, Djaldetti R, Luckman J, Dabby R. Thoracic sensory level as a false localizing sign in cervical spinal cord and brain lesions. Clinical Neurology and Neurosurgery 2013;115(January (1)):54–6. [2] Starr A. Sensory evoked potentials in clinical disorders of the nervous system. Annual Review of Neuroscience 1978;1:103–27. Review. [3] Rossini PM, Gigli GL, Zarola F, Marciani MG, Caramia M, Bernardi G. On the spinal pathways mediating scalp-SEPs to upper and lower limb nerve stimulation: case report and discussion. Acta Neurologica Scandinavica 1986;74(September (3)):230–4. [4] Schwartz DM, Sestokas AK, Dormans JP, Vaccaro AR, Hilibrand AS, Flynn JM, et al. Transcranial electric motor evoked potential monitoring during spine surgery: is it safe? Spine (Phila Pa 1976) 2011;36(June (13)):1046–9.
Hakan Akgün ∗ Etimesgut Military Hospital, Department of Neurology, Ankara, Turkey Mehmet Yücel Kasımpas¸a Military Hospital, Department of Neurology, Istanbul, Turkey O˘guzhan Öz S¸eref Demirkaya Gülhane Military Medical Academy, Department of Neurology, Ankara, Turkey
∗ Correspondence address: Comprehensive Epilepsy Center, New York-Presbyterian Hospital, Weill Cornell Medical Center, 525 East, 68th Street, New York, NY 10065, USA. Tel.: +1 212 746 2346; fax: +1 212 746 8845. E-mail address: [email protected]
23 February 2013 Available online 18 March 2013 http://dx.doi.org/10.1016/j.clineuro.2013.02.022
Scrotal swelling due to migration of the abdominal catheter of a cyst-peritoneal shunt Keywords: Scrotal Swelling Cyst-peritoneal shunt
Dear Editor,
∗ Corresponding
author. Tel.: +90 312 2491011; fax: +90 312 3044475. E-mail addresses: [email protected], [email protected] (H. Akgün) 13 January 2013 Available online 5 March 2013
http://dx.doi.org/10.1016/j.clineuro.2013.02.011
Electrophysiological mapping for eloquent cortex during awake craniotomy
A 30-year-old man presented with a history of left scrotum swelling for over a week without fever. There was no previous history of epididymitis or orchitis and physical examination revealed no palpable inguinal hernia. His past medical history revealed a cystic-peritoneal (C-P) shunt placement 6 months ago because of a large arachnoid cyst of the left middle cranial fossa [Fig. 1]. A shunt series was performed and abdominal X-ray demonstrated the caudal end of the shunt to project over the left scrotum [Fig. 2], suggesting shunt migration. The patient was taken up for exploratory laparotomy and the peritoneal catheter was repositioned. Prophylactic obliteration of the patent processus vaginalis was performed to prevent recurrence. The patient was regularly followed up at
Keywords: Cortical mapping Awake craniotomy
Dear Editor, I read with interest Chacko et al. [1] experience on awake craniotomy with electrophysiological mapping for resection of eloquent area tumors. Ideally the lowest current which elicits a positive response indicates presence of eloquent cortex. The threshold for eliciting a response depends upon the proximity of the cortical stimulator to the eloquent cortex and also the intensity of the stimulating current. Set the stimulating current too high and you risk a false positive result due to spread of current to adjacent eloquent cortex thus potentially limiting the extent of the surgery. Set the current too low and you risk a false negative response with resultant inadvertent damage to eloquent brain tissue. Will the authors please comment on their stimulation techniques and experience with the same. Did they find that one approach fits all or did they modify their technique based on type of eloquent cortex and preoperative imaging showing extensive distortion of brain architecture and mass effect?
Reference [1] Chacko AG, Thomas SG, Babu KS, Daniel RT, Chacko G, Prabhu K, et al. Awake craniotomy and electrophysiological mapping for eloquent area tumours. Clinical Neurology and Neurosurgery 2013;115:329–34.
Fig. 1. CT scan demonstrating shunt catheter placement in a left middle cranial fossa arachnoid cyst.