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Electromyographic monitoring for pedicle screw placements

13.1 Introduction Through the ages, various treatments for spinal deformity have evolved. In 1962, Harrington ushered in the revolutionary utilization of metallic, internal fixation devices for spinal deformity when he reported on the utilization of a distraction rod construct for the treatment of scoliosis. In 1982, Luque demonstrated how spinal deformity could be corrected by the utilization of segmental fixation and the application of transverse forces.…

Neurophysiological identification of long sensory and motor tracts within the spinal cord

12.1 Introduction Intraoperative neurophysiological monitoring of the functional integrity of spinal cord (SC) pathways is crucial to prevent, limit, or document the moment of surgically induced injury . The available methods can be divided into monitoring and mapping techniques . Monitoring methods are applied to continuously assess the functional integrity of the tracts in the white matter and/or synaptic circuits in the gray matter. Monitoring modalities…

Brain stem mapping

11.1 Introduction Advanced technology of both surgery and diagnostic imaging opened the door to the brain stem which was once regarded as “no man’s land” . Brain stem mapping (BSM) is now considered a tool in the neurophysiological armamentarium available during surgeries for brain stem lesions that often place cranial nerve motor nuclei (CMN) at risk for injury . Historically, auditory brain stem responses (ABRs) and…

Cortical and subcortical brain mapping

9.1 Introduction In modern neuro-oncology the two main goals are maximizing the extent of tumor resection to improve survival and avoiding postoperative deficits to improve the quality of life . Therefore tumor resection should be based on functional boundaries rather than anatomy alone . Complete removal or gross total resection (GTR) remains the surgical goal for most intracranial tumors including gliomas, and there is increasing evidence…

Effects of subthreshold stimuli on the excitability of axonal membrane

8.1 Introduction The action potential, initiated by the depolarization of the axonal membrane, has classically been described as having periods of both hypo- and hyperexcitability . Historically, most investigations related to axonal excitability use paired stimuli by first applying a test stimulation pulse (usually of suprathreshold intensity) and then a conditioning stimulus pulse (a percentage of that test stimulus) . Bostock and Trevillion have described that…

Neurophysiology of language and cognitive mapping

7.1 Introduction Language and cognitive mapping is recommended in patients with intrinsic tumors involving language or cognitive pathways. Traditionally, this type of mapping was limited to patients harboring lesions in the so-called dominant hemisphere, where language was thought to be uniquely located. Nowadays, however, due to the evolving knowledge of language and cognitive network organization, mapping has been extended also to patients with tumors located in…

Intraoperative neurophysiological monitoring of the sacral nervous system

6.1 Introduction The functions involving the genitourinary and the anorectal systems are uniquely controlled by the complex interaction of the autonomic and the somatic nervous systems. Insofar as it is the sacral parasympathetic and somatic systems that comprise the most important peripheral nervous structures controlling these functions, they may also be referred to as sacral functions . The functions themselves (micturition, defecation, erection, etc.) are now…

Neurophysiology of the auditory system: basics and ION techniques

5.1 The auditory nerve Introduction of intraoperative monitoring of the hearing function in the 1980s has reduced the incidences of hearing loss as a complication to surgical operations that affect the auditory nerve considerably. The auditory nerve was one of the first cranial nerves to be monitored routinely in neurosurgical operations . There are three ways in which the function of the auditory nerve can be…

Neurophysiology of the visual system: basics and intraoperative neurophysiology techniques

4.1 Introduction Neurosurgical procedures for treatment of tumors or vascular lesions along the visual pathways carry a risk of damage to the visual pathways. These procedures include parasellar tumors, pituitary adenomas, craniopharyngiomas, and tuberculum sellae meningiomas. Risk of visual impairment also exists in surgeries involving temporal and occipital lobe tumors as well as intraorbital lesions. Additionally, surgical intervention for the treatment of aneurysms, such as internal…

Monitoring somatosensory evoked potentials

3.1 Introduction Intraoperative somatosensory evoked potential (SEP) monitoring selectively helps reduce the risk of injuring the dorsal somatosensory system for proprioception, vibration sense, and discriminative touch . It also complements motor evoked potential (MEP) monitoring of surgeries mainly risking corticospinal motor injury . In addition, when MEPs are not done SEPs can still indirectly help avoid motor injury because of sensory and motor system proximity ,…

Intraoperative neurophysiology and methodologies used to monitor the functional integrity of the motor system

2.1 Intraoperative monitoring of the motor system: a brief history 2.1.1 Penfield’s time When discussing the use of intraoperative electrical stimulation of the upper motoneurons in humans, it is essential to mention Wilder Penfield (1891–1976). His publication with Edwin Boldrey in the journal Brain summarized his work on the motor and somatosensory system’s organization of the cerebral cortex in humans, as explored with intraoperative electrical stimulation.…

Animal and human motor system neurophysiology related to intraoperative monitoring

1.1 Introduction The uses of monitoring motor responses for stimulating the human cerebral cortex have clearly expanded beyond the clinical mapping studies of the exposed brain at operation . The discovery that transcranial electrical stimulation (TES) of human motor cortex could cause muscle activation and its replacement in (awake) humans by the less painful transcranial magnetic stimulation (TMS) greatly expanded the opportunities for motor pathway monitoring.…

Functional MR Imaging

History of Functional Magnetic Resonance Imaging While conventional MRI (magnetic resonance imaging) and CAT (computerized axial tomogram) scan image the structural anatomy of the brain (and pathology) to a high degree of spatial resolution, functional imaging has carried this imaging capability one step further by imaging the functional activity in the brain, the ability to dynamically image functional activity in the brain at a significantly higher…

Cognitive Function Monitoring

The hardest thing of all is to find a black cat in the dark room especially if there is no cat. Kung Fu Tzu Cognitive function is an intellectual process by which one becomes aware of, perceives, or comprehends ideas. It involves all aspects of perception, thinking, reasoning, and remembering. The word origin comes from Latin verb “cognosco,” literally meaning being able “to conceptualize” or “to…

Brain Tissue Oxygenation

Introduction Primary brain injury results from traumatic or disease-related impact. Two major problems are associated with these injuries. First, damage after primary brain injury cannot be undone even with the best possible management. Second, secondary brain injury is inherent due to a variety of cellular processes. Hence, avoiding secondary brain injury due to hypoxia and/or ischemia is the mainstay and declared goal of neurocritical care. Historically,…

Brain Microdialysis

Introduction Sampling of the cerebral tissue environment to gain clinical insight into the state of a patient's evolving neurologic health is an evolving trend in neuroscience and critical care medicine. A start to this can be traced back to Ungerstedt and Pycock; when in 1974, they published a paper studying the biochemistry of dopamine in the animal brain. They not only looked at animal behavior and…

Near-Infrared Spectroscopy

Introduction Cerebral oximetry is a noninvasive monitoring modality based on several physical principles that basically acts as an indirect indicator of perfusion adequacy. Therefore, it allows continuous information on oxygen supply-versus-demand balance. It has numerous applications in the clinical field but also in research. This monitor is now being evaluated in a variety of different clinical areas, mostly adult and pediatric cardiac surgery, as well as…

Evoked Response Monitoring

Introduction Monitoring of the central nervous system using evoked responses allows assessment of neural tracts that are normally silent during coma or anesthesia. This differs from the electroencephalogram (EEG), which monitors spontaneous activity. They are not a replacement for awake testing such as performed during awake craniotomy or under local anesthesia, but they allow examination during general anesthesia. This chapter will discuss the techniques of the…

Transcranial Doppler Ultrasonography

Introduction Monitoring the cerebral blood flow (CBF) is critical not only in patients with known neurological disease but also in patients at risk of neurological damage in the perioperative period. Despite the fact that virtually all interventions in neuroanesthesia and neurointensive care are directed toward maintaining adequacy of cerebral perfusion, perioperative monitoring of the same is limited because of technical and logistic issues. Introduced by Aaslid,…