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Monday, May 28, 2007

Brain Mapping & Electro-corticography?

What is brain Mapping??, what are the types of recording system available to record selective areas of the brain during brain surgery. Dr.Anschel, MD reviews the available techniques
Electro-corticography Systems in Surgery of the Brain
Technology Spotlight

David J. Anschel, M.D.
Contributing Editor
The human brain is a fantastically complicated organ. On any given day, the average man does not give much thought to this 3 pound; blood gorged, gelatinous mass stuck on his shoulders.
However, the brain is responsible for controlling nearly ever human behavior and action. It is the source of all human creativity and accomplishments and everything mankind will ever achieve.
It has long been known that all of this fascinating power is not distributed evenly throughout its neuronal interweave. Most brain functions are based in discreet areas, and often brain dysfunction occurs focally.
  • These facts are critical to the modern neurosurgical approach to disease and are the basis for electrocorticography. The process of recording brain electrical activity directly from the exposed brain surface using electrodes, electrocorticography is most often used to precisely localize critical brain structures in order to avoid them when operating upon diseased areas of the brain.
    Additionally, electrocorticography is particularly useful while planning epilepsy surgery, as the onset and electrical propagation of a seizure may be mapped accurately. Electrocorticography may be used intraoperatively or at the bedside.

Tuesday, May 8, 2007

Benign Or Metastatic Tumor Removal &The importance of IntraOperative Neuromonitoring

Resection of a benign brachial plexus nerve sheath tumor using intraoperative electrophysiological monitoring.

Kwok K, Davis B, Kliot M.
Department of Neurosurgery,
University of California at Davis, Sacramento, California 95825, USA. keithkwok2004@yahoo.com

OBJECTIVE: Benign peripheral nerve sheath tumors arising from the brachial plexus are rare. Neurosurgeons often lack the clinical and surgical experience to optimize the management of these uncommon tumors. We filmed a video depicting the surgical resection of a benign peripheral nerve sheath tumor involving the brachial plexus. METHODS: An illustrative case was used to demonstrate the proper management of a brachial plexus nerve sheath tumor including the important role of intraoperative electrophysiological neuromonitoring during tumor resection. RESULTS: Using an illustrative case, we describe a systematic approach in the evaluation and surgical management of patients with a brachial plexus nerve sheath tumor. The importance of taking a thorough clinical history, performing a thorough physical examination, applying high-resolution magnetic resonance imaging techniques to visualize the pathology, and using intraoperative electrophysiological neuromonitoring during surgical exposure and resection of the tumor are stressed. Combined with appropriate postoperative treatment, these techniques minimize the risks and increase the likelihood of achieving a good clinical outcome. CONCLUSION: Brachial plexus nerve sheath tumors are challenging mass lesions that should be evaluated and surgically resected by an experienced team of physicians to optimize clinical outcome.

Neuromonitoring during surgery for metastatic tumors to the spine: intraoperative interpretation and management strategies.
Quiñones-Hinojosa A, Lyon R, Ames CP, Parsa AT.

Department of Neurological Surgery,
Brain Tumor Research Center, University of California-San Francisco,
505 Parnassus Avenue, M-779, San Francisco, CA 94143-0112, USA.

Resection of metastatic tumors of the spine poses great technical challenges, with the potential of creating severe neurologic deficits. Several modalities of electrophysiologic monitoring, including SSEPs and MEPs, have evolved to aid in resection of these tumors. This review has presented additional techniques-such as mapping of the dorsal columns with antidromic-elicited SSEPs to plan the myelotomy and direct intra-medullary stimulation-that help to identify the extent of the tumor margin at its interface with functional tracts. Neuromonitoring can potentially minimize the sensory and motor damage that can occur during resection of metastatic tumors of the spine. Further experience with these techniques should allow improved results follow-ing surgical procedures in functionally eloquent are as of the spinal cord during the surgical management of metastatic tumors

Sunday, May 6, 2007

Regeneration: Sensory vs Motor nerves?

Comparison of the fastest regenerating motor and sensory myelinated axons in the same peripheral nerve
Mihai Moldovan1, Jesper Sørensen1,2 and Christian Krarup1,

Brain 2006 129(9):2471-2483; doi:10.1093/brain/awl184

Functional outcome after peripheral nerve regeneration is often poor, particularly involving nerve injuries far from their targets. Comparison of sensory and motor axon regeneration before target reinnervation is not possible in the clinical setting, and previous experimental studies addressing the question of differences in growth rates of different nerve fibre populations led to conflicting results. We developed an animal model to compare growth and maturation of the fastest growing sensory and motor fibres within the same mixed nerve after Wallerian degeneration. Regeneration of cat tibial nerve after crush (n = 13) and section (n = 7) was monitored for up to 140 days, using implanted cuff electrodes placed around the sciatic and tibial nerves and wire electrodes at plantar muscles. To distinguish between sensory and motor fibres, recordings were carried out from L6–S2 spinal roots using cuff electrodes. The timing of laminectomy was based on the presence of regenerating fibres along the nerve within the tibial cuff. Stimulation of unlesioned tibial nerves (n = 6) evoked the largest motor response in S1 ventral root and the largest sensory response in L7 dorsal root. Growth rates were compared by mapping the regenerating nerve fibres within the tibial nerve cuff to all ventral or dorsal roots and, regardless of the lesion type, the fastest growth was similar in sensory and motor fibres.

Wednesday, May 2, 2007

Medical Breakthroughs-WILX MSNBC news

Intraoperative Neuromonitoring System
Reporter: Jessica Aspiras
Email Address: jessica.aspiras@wilx.com
"We want to make sure that all parts of the nervous system stay functioning," says Ingham Regional Medical Center neurophysiologist James Watt.
The nervous system includes the sensory and motor systems - the two parts that make up the spinal cord. During surgical procedures that involve portions of the neck, back, and carotid arteries, the Intraoperative Neuromonitoring System is crucial. And IRMC, it now has an in-house staff to operate it.

Propofol- Impaired thalamic responses to sensory stimuli??

Propofol suppresses synaptic responsiveness of somatosensory relay neurons to excitatory input by potentiating GABAA receptor chloride channels
Shui-Wang Ying1 and Peter A Goldstein
Mol Pain. 2005; 1: 2, 2005 January 14. doi: 10.1186/1744-8069-1-2.

Propofol is a widely used intravenous general anesthetic. Propofol-induced unconsciousness in humans is associated with inhibition of thalamic activity evoked by somatosensory stimuli. However, the cellular mechanisms underlying the effects of propofol in thalamic circuits are largely unknown. We investigated the influence of propofol on synaptic responsiveness of thalamocortical relay neurons in the ventrobasal complex (VB) to excitatory input in mouse brain slices, using both current- and voltage-clamp recording techniques. Excitatory responses including EPSP temporal summation and action potential firing were evoked in VB neurons by electrical stimulation of corticothalamic fibers or pharmacological activation of glutamate receptors. Propofol (0.6 – 3 μM) suppressed temporal summation and spike firing in a concentration-dependent manner. The thalamocortical suppression was accompanied by a marked decrease in both EPSP amplitude and input resistance, indicating that a shunting mechanism was involved. The propofol-mediated thalamocortical suppression could be blocked by a GABAA receptor antagonist or chloride channel blocker, suggesting that postsynaptic GABAA receptors in VB neurons were involved in the shunting inhibition and such inhibition may contribute to the impaired thalamic responses to sensory stimuli seen during propofol-induced anesthesia.

Ulnar and Tibial Nerves- Neuromonitoring?

Ulnar Nerve:
Ulnar nerve is important to monitor during Peripheral Neuropathy, ulnar nerve palsy (if a single ulnar nerve involved, it is called mononeuropathy?)

Ulnar nerves for upper and Tibial Nerves for lower sensory evoked potentials (SSEPs) are the most commonly used nerves, normally pad electrodes are placed for stimulation and the resulting sensory activities are recorded at the scalp sites using needle electrodes.

Ulnar nerve damage due to fractures or other causes can affect the movement and sensation in the hands and palm, the image (ADAM) shows the ulnar nerve damage due to fracture, the image also shows the trajectory of ulnar nerve. It originates from the brachial plexus and travels down the arm. Any compression of brachial plexus due to prolonged pressue on elbow or fracture of elbow could cause ulnar nerve damage. Ulnar nerve is most commonly used to monitor upper extremities during cervical spinal surgeries.

Tibial Nerve:

Sunday, April 29, 2007

Research & Case Studies using Neuromonitoring!

Years: 2005-2007
Neuromonitoring in Infants:
Motor Evoked Potentials After Transcranial Magnetic Stimulation Support Hypothesis of Coexisting Central Mechanism in Obstetric Brachial Palsy.
Six infants with obstetric brachial palsy, ranging from 4 to 7 months of age, were investigated. One was suspected of having extensive brachial plexus lesions and five were suspected of having a unilateral lesion of both roots C5 and C6. All were referred to our center to investigate the possibility for reconstructive surgery. In all infants, even at this age, transcranial magnetic stimulation resulted in motor evoked potentials (MEP) in the biceps (in one, in the brachioradial) muscles. Averaging could not be done because of the intraindividual variation in latency. The MEP was easier to recognize if evoked when the infant had the arm bent. In all five infants suspected of upper brachial plexus lesion with avulsion of both roots C5 and C6 and/or complete rupture of the upper trunk, proven in four, an MEP on the lesioned side could be evoked. Combined with earlier investigations showing (almost) normal EMG and somatosensory evoked potentials in infants with upper plexus lesion, this leads us to the conclusion that the paralysis of these infants cannot only be attributed to the peripheral axonal damage alone but that central plasticity must also play an important role. As this is a slow process, some infants might not yet be able to use the paralytic muscles. Some theoretic issues are discussed.

Neuromonitoring in Young Child:
Improvement of Motor-Evoked Potentials by Ketamine and Spatial Facilitation During Spinal Surgery in a Young Child.
Anesth Analg 2005;100:1634-1636© 2005
International Anesthesia Research Society
Monitoring motor evoked potentials is desirable during spine surgery but may be difficult to obtain in small children. In addition, the recording of reliable signals is often hampered by the presence of various anesthetics. We report the case of a young child whose motor evoked potentials were successfully monitored using a ketamine-based anesthesia and a newly introduced stimulation technique consisting of combined spatial and temporal facilitation.

Journal of Clinical Neurophysiology.
February 2007. Colon, A J. *; Vredeveld, J W. *+; Blaauw, G ++

Is MEP monitoring is superior to SSEP in detecting nerve damages?

Our data again confirm that MEP monitoring is superior to SSEP monitoring in detecting impending impairment of the functional integrity of cerebral and spinal cord motor pathways
during surgery. Detection of MEP changes and adjustment of the surgical strategy might allow to prevent irreversible pyramidal tract damage. Stable SSEP/MEP recordings reassure the surgeon that motor function is still intact and surgery can be continued safely. The combined SSEP/ MEP monitoring becomes advantageous, if one modality is not recordable.

Neurosurgical Review
Springer Berlin, Volume 30, Number 2 / April, 2007
M. R. Weinzierl, Email: Martin.Weinzierl@ukaachen.de

Posterior thoracic segmental pedicle screw instrumentation: Evolving methods of safe and effective placement
Intraoperative neuromonitoringIntraoperative neuromonitoring (IONM) has become an integral part of complex spine surgery. The primary objective of IONM is to provide the surgeon with early warning of a potential neurological event. IONM, in the form of somatosensory-evoked potentials (SSEP's), initially gained popularity with deformity surgeons who routinely relied on the Stagnara wake up test to monitor neurologic integrity. Monitoring techniques have become much more sophisticated since their inception affording a higher level of protection to the patient. At present, many centers employ SSEP's, motor-evoked potentials (MEP's), and spontaneous and triggered EMG responses during complex thoracic pedicle screw instrumentation procedures.

Neurology India
Year : 2005 Volume : 53 Issue : 4 Page : 458-465
Philadelphia, 19107 USA

Years 2000-2005

Intraoperative Neuromonitoring.
Article Neurologist. 8(4):209-226, July 2002.

Minahan, Robert E. MD
BACKGROUND-: Intraoperative neuromonitoring (IONM) has been a valuable part of surgical procedures for over 25 years. Insight into the nervous system during surgery provides critical information to the surgeon allowing reversal or avoidance of neural insults.

REVIEW SUMMARY-: Electrophysiological tests including electroencephalography, electromyography, and multiple types of evoked potentials (somatosensory, auditory, and motor) are monitored during surgeries that involve risk to the nervous system. Deterioration of signals suggests a surgical insult and is associated with an increased risk of postoperative deficit. Intraoperative identification of this risk allows corrective action. In addition, IONM teams make use of their armamentarium of tests to evaluate anatomy or function of the nervous system in response to specific questions posed by the surgical team.

CONCLUSIONS-: Intraoperative recordings are now a routine part of many surgical procedures. Their correct application leads to improved surgical outcome.
(C) 2002 Lippincott Williams & Wilkins, Inc

Years 1990- 2000

Years 1980-1990

Years 1970-1980

The Inception of Neuromonitoring: 1960