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Intraoperative neurophysiological monitoring during microvascular decompression of cranial nerves

33.1 History Over the years, several neurological disorders have been identified as being caused by pulsatile vascular compression of centrally myelinated cranial nerves. Symptoms are thought to occur as the arteries of the base of the brain elongate and loop with aging so that they impact the nerves. The brain also moves caudally in the posterior fossa with aging contributing to arterial and venous pulsatile compression…

Surgery for epilepsy

32.1 Introduction Epilepsy has been recognized as a serious medical condition for thousands of years . Estimates of its prevalence range from 0.5% to 1%; thus 30–80 million people suffer from epilepsy. Despite this, medical therapies fail in up to 30% of patients. On the other hand, surgical therapies in selected patients whose seizures that cannot be controlled with medications have a 50%–75% cure rate .…

An intraoperative neurophysiological monitoring method for testing functional integrity of the low extremity peripheral nerves during hip surgery

31.1 Introduction Peripheral nerve injury is a serious potential complication in hip procedures, which may result in postoperative permanent sensory and/or motor deficits. The incidence of sciatic nerve palsy after hip surgery ranges from 0.3% to 4% in primary total hip arthroplasty (THA) up to 7.6% in revision surgery or developmental dysplasia of the hip (DDH) However, Weber in 1976 found evidence of subclinical nerve injury…

Intraoperative neurophysiology of the peripheral nervous system

30.1 Background Over the course of the last four decades, there has been increasing interest in assessing segments of peripheral nerve during surgery. For example, the surgeon confronted by a neuroma in continuity has difficult decisions to make. He must determine the status of the nerve at the time of surgery and judge its potential to recover from injury. He must decide the best course of…

Neurophysiological monitoring during endovascular procedures on the spine and the spinal cord

29.1 Spinal cord vascularization and ischemia 29.1.1 Vascular anatomy of the human spinal cord Before describing the role of neurophysiological monitoring during endovascular procedures aimed to treat spinal hypervascular lesions, an overview on the vascular anatomy of the normal spinal cord is mandatory. While we refer the reader to classical textbooks and articles for a detailed analysis of the vascular anatomy and the wide range of…

Intraoperative neuromonitoring and complex spine surgery

28.1 Introduction While surgical interventions upon the spine have been performed since ancient times, there has been an exponential increase in the number of spine surgeries over the past 35 years. There are many reasons for this phenomenon: increasing longevity, changing expectations of the elderly population regarding physical activity and technical advances in several fields, from metallurgy to anesthesiology to radiological imaging, enabling more aggressive surgeries…

Intraoperative neurophysiological monitoring in tethered cord surgery

27.1 Introduction Tethered cord syndrome (TCS) is a complex and progressive clinical and radiological condition, secondary to an embryologic failure of spinal cord development, which induces various types of spinal dysraphisms. These defects ultimately cause a radicular-medullary stretch that generates a hypoxic-ischemic damage to the nervous structures of the conus–cauda region. This distress may lead to functional disorders, which tend to worsen with age . It…

Surgery for intramedullary spinal cord tumors and syringomyelia

26.1 Introduction With good reason neurosurgeons continue to have great respect for the spinal cord. In particular, the resection of intramedullary tumors is believed to carry a high risk for surgical damage and subsequent neurological dysfunction because the cord is such a delicate structure with tightly packed essential pathways and neural circuits. Surgical manipulation inside the cord involves the risk for selective damage to either the…

Carotid endarterectomy

25.1 Introduction Up to 20% of all ischemic strokes are caused by an occlusion of the extracranial part of the internal carotid artery (ICA) . The higher the degree of the carotid artery stenosis, the more likely is the occurrence of neurologic deficits due to a reduction of cerebral perfusion pressure. The prevalence of extracranial ICA stenosis was shown to be gender specific and related to…

Surgery of the face

24.1 Introduction In 1829, the surgeon and artist Sir Charles Bell stated that the facial nerve (FN) is the nerve of “anatomy expression” . The FN has two entirely distinct functions in humans and high primates. The first comprises essential somatomotor functions such as eye protection through the blink reflex, keeping the food inside the mouth cavity, assisting in speech. The second function is the facial…

Continuous dynamic mapping during surgery of large vestibular schwannoma

Abbreviations CMAP compound muscle action potential CN VII cranial nerve VII or facial nerve CPA cerebellopontine angle HBS House–Brackmann score MEP motor-evoked potential VS vestibular schwannoma 23.1 Introduction In vestibular schwannoma (VS) surgery, postoperative facial nerve (CN VII) palsy is an important neurological deficit and a stigma that significantly reduces the quality of life. In 25%–70% of patients who have undergone complete removal or gross total…

Surgery of brainstem lesions

22.1 Introduction In 1939, Bailey et al. described the treatment of brainstem gliomas as “a pessimistic chapter” in the history of neurosurgery . Thirty years later, Matson stated, “regardless of specific histology (they) must be all classified as malignant tumors, since their location in itself renders them inoperable” . Traditionally, all tumors involving the brain stem were considered infiltrative with diffused glial proliferation. Therefore in consideration…

Surgery and intraoperative neurophysiological monitoring for aneurysm clipping

21.1 Introduction Intraoperative neuromonitoring for aneurysm surgery follows the rationale to detect pending ischemia related to the vascular territories of interest. First reports about neuromonitoring in intracerebral aneurysm surgery date back into the mid-1980s, where solely somatosensory potentials have been used . This followed encouraging animal studies demonstrating a relation between electroencephalography, somatosensory potentials, and cerebral perfusion. Reports about sustained somatosensory-evoked potential (SEP) but postoperative motor…

Surgery of brain tumors asleep

20.1 Introduction In surgery of supratentorial brain tumors, prompt and complete resection offers the most favorable outcome; however, damage to essential cortico-subcortical structures may cause permanent neurological deficits . The surgeon faces a complex balance between radicality of resection and preservation of function: this is of particular importance in the surgery of gliomas, which exposes the patient to significant morbidity and, often, short life expectancy .…

Functional approach to brain tumor surgery: awake setting

19.1 Introduction About 20,000 people/year are diagnosed with primary brain cancers in Europe. The 5-year survival rate is around 33%, additionally there is an extensive socioeconomic costs . Gliomas are the most common primary brain tumors. Historically they have been divided into low-grade and high-grade gliomas. Recent advances in molecular biology divide gliomas in two groups based on the presence of the IDH1 mutation. Gliomas in…

The posterior root-muscle reflex

18.1 Introduction Posterior root-muscle (PRM) reflexes are short-latency spinal reflexes evoked by the electrical stimulation of lumbar and upper sacral posterior rootles/roots and recorded from various lower limb muscles . Posterior root fibers can be stimulated in humans by electrodes surgically placed in the posterior epidural space [epidural spinal cord stimulation (SCS) ], by stimulating needle electrodes inserted into the epidural space , and by noninvasive…

Blink reflex

17.1 Introduction The closing of eyelids in response to various stimuli is a blink reflex (BR). In humans and primates this closing of eyelids is bilateral while in other animals, especially those with lateralized position of the eyes, it is frequently unilateral. Clinically, the BR is elicited after a gentle brush to the cornea or the eyelashes or after a glabelar percusion . I n 1952,…

Bringing the masseter reflex into the operating room

16.1 Introduction A reflex is a relatively simple motor behavior reflexively driven by afferent inputs of diverse modalities. The term “reflexively” refers to the fact that this motor response is not subjected to conscious voluntary control, although it may be subjected to modulation by higher CNS structures. Brainstem reflexes can be a window for understanding how the brainstem works. The masseter reflex is a monosynaptic proprioceptive…

Intraoperative monitoring of the vagus and laryngeal nerves with the laryngeal adductor reflex

15.1 Introduction Brainstem reflexes are relatively simple motor responses organized by the brainstem and designed to enable the body to adjust rapidly to sudden changes in the environment. The laryngeal adductor reflex (LAR) is possibly one of the most crucial of all brainstem reflexes because of its life-sustaining, pivotal role in airway protection. The LAR protects the airway from potentially life-threatening aspiration by causing vocal fold…

Clinical and neurophysiologic features of the pure motor deficit syndrome caused by selective upper motor neuron lesion: contribution to a new neurological entity

14.1 Introduction Almost 60 years ago, the first description of pure motor hemiplegia of supraspinal origin was published by Fisher and Curry . Their definition was as follows: “For present purposes a pure motor hemiplegia is defined as a paralysis complete or incomplete of the face, arm and leg on one side unaccompanied by sensory signs, visual field defect, dysphasia or apractagnosia.” “In the case of…