Microbiology

Infection of the central nervous system can be due to a variety of pathogenic agents that include bacteria, viruses, fungi, and parasites. Several sensitive and specific diagnostic tests are now available that allow for the rapid and accurate identification of the offending organism. The widespread indiscriminate use of some antibiotics has resulted in the emergence of organisms that are resistant to those agents at an alarming rate. The prevention of a neurosurgical site infection is usually possible with the use of prophylactic antibiotics and through careful attention to surgical technique. Controversy surrounds several issues in neurosurgical practice such as preoperative surgical site preparation, antimicrobial prophylaxis, and the surgical and medical management of postoperative infections. Only after the causative microbe is determined and the appropriate surgical and medical management is initiated can you hope to achieve the optimal clinical outcome leading to a reduction in neurological morbidity and mortality.

Arachnoid cysts

First described in 1831, arachnoid cysts are cerebral spinal fluid-filled spaces lined with arachnoid membrane. They account for 1% of all intracranial space occupying lesions and can also be found rarely in the spinal column. Most intracranial arachnoid cysts are found in the middle cranial fossa with a male predilection and a slight preponderance for the left side. With the availability of modern imaging, many more arachnoid cysts are being picked up incidentally in asymptomatic patients. However, symptomatic arachnoid cysts are predominantly found in the paediatric population with patients typically presenting with headaches, rapid head growth, developmental delay, and seizures. Treatment of patients with asymptomatic arachnoid cysts has typically been conservative management with surgery only considered in patients with symptoms. Surgical management remains controversial and includes open techniques, endoscopic fenestration of cyst, or shunting procedures.

Shunt technology and endoscopic ventricular surgery

The management of cerebrospinal fluid (CSF) disorders via CSF diversion is now a complex clinical science, requiring a detailed understanding of CSF physiology in both the normal and diseased brain. Successful treatment of this group of disorders requires a comprehensive knowledge of all the available shunt types, their similarities, differences, and idiosyncrasies. The rapid development of endoscopic neurosurgical techniques makes treating this group of patients without a shunt often a real possibility, and arguably is now a core neurosurgical skill. In this chapter we will summarize the CSF physiology in the normal state, and explain the principles of CSF diversion before going on to describe the various shunt types available. A section will be devoted to endoscopic CSF diversion techniques, including a detailed explanation of third ventriculostomy.

Spinal development and spinal dysraphism

The term spinal dysraphism encompasses a group of congenital disorders of spinal cord development. This potentially confusing array of conditions is best understood from an embryological perspective, and a unifying method of classification is presented. Spinal dysraphism is associated with neurological, urological, and orthopaedic deficits, these may be present at birth or may evolve over time due to the effects of spinal cord tethering. Precise diagnosis is essential to formulating an appropriate surgical management plan in order to optimize long-term neurological outcome. Contemporary and controversial surgical advances in the field are discussed including electrophysiology directed radical resection for spinal lipomas and antenatal surgery for myelomeningocele.

Developmental disorders of the brain

Prenatal and postnatal development of the brain is controlled by a multiplicity of genetic mechanisms. Genetic abnormalities and environmental insults are responsible for a bewildering array of developmental disorders associated with brain malformations. Classic embryology remains key to understanding these, and an appreciation of the processes of gastrulation, dorsal and ventral induction, neuronal differentiation, proliferation, histogenesis, and migration and myelination will help the neurosurgeon understand the conditions likely to be encountered in clinical practice. In this chapter the more common and many less common brain malformations are reviewed. These include anencephaly, holoprosencephaly, septo-optic dysplasia, schizencephaly, grey matter heterotopias, lissencephaly/pachygyria, polymicrogyria, porencephaly, developmental anomalies of the corpus callosum, microcephaly, hemimegalencephaly, and posterior fossa malformations. The emphasis is on promoting an understanding of concepts and on clinical implications, rather than on imparting detail.

Classification of seizures and epilepsy

Epileptic seizures are transient neurologic alterations due to abnormal excessive or synchronous neuronal cerebral activity. They may cause subjective symptoms (aura), and objective autonomic, behavioural, or cognitive alterations in any combination. Focal seizures are initially generated in one circumscribed area in the brain, whereas generalized seizures involve bihemispheric neuronal networks from the seizure onset. Epilepsy is a brain disease defined by the occurrence of two unprovoked seizures more than 24 h apart or one unprovoked seizure with underlying pathological or genetic factors resulting in a similar recurrence risk. Focal epilepsy syndromes are best classified by aetiology or anatomical area of origin. A seizure that does not self-terminate results in status epilepticus, and constitutes a medical emergency that requires immediate treatment. Focal cortical dysplasia and hippocampal sclerosis are the commonest aetiologies of epilepsy amenable to surgical treatment and are reviewed here. The limbic pathway may be involved in seizure propagation, and the anatomy is described.

Peripheral nerve tumours

This chapter on peripheral nerve sheath tumours (PNSTs) explores the pathology, clinical presentation, investigation, management, and outcomes of both benign and malignant peripheral nerve sheath tumours (MPNSTs). The focus is centred upon the more commonly encountered tumours: schwannoma, neurofibroma, and perineurioma. Significant emphasis is also given to the rarer but life-threatening MPNSTs. It aims to equip the reader with the latest information available in the literature with regards to PNSTs occurring sporadically or in association with inherited conditions. Up to date investigation and management options available are also presented. With the detailed insights provided, the aim is to ensure that the reader would be confident in managing patients presenting with peripheral nerve tumours.

Cervical spine injuries

The management of cervical spine fractures is a complex and fascinating topic. A multitude of descriptive terminologies and classification systems have been developed over the years in an attempt to better understand this heterogenous group of patients. Despite this however, there is often little consensus with regards to the best way to manage this population. This chapter will predominantly discuss the decision-making process involved in the management of cervical spine fractures. The goal of the spine surgeon in managing patients with acute cervical spine injury is to prevent secondary neurological injury, deformity, and pain by re-establishing stability if necessary. Assessing how to achieve this goal can be very challenging. The surgeon will be faced with many questions. Which patients should undergo surgical intervention? Which operation will best stabilize the spine? Which patients should be treated with a collar or a halo vest? Does the injury require reduction with traction initially? There are also questions of timing. When should the surgeon plan the proposed procedure?

Managing spinal cord trauma

Spinal cord injury (SCI), either traumatic or non-traumatic in aetiology, leads to temporary or permanent damage to the spinal cord function. Significant efforts have been directed towards the elucidation of the underlying pathophysiology of SCI. Both primary and secondary mechanisms of SCI exist, leading to immediate and often irreversible cell damage. Immediate treatment and adequate management in the setting of acute SCI are essential, preservation of even a small amount of functional neuronal tissue can permit ambulation. SCI is associated with a prolonged hospital stay, rehabilitation stay, and often associated with enormous monetary costs. Neurological recovery after SCI is largely dependent on the extent of injury. The management of SCI and the determination of the role and timing of surgical decompression remain crucial and yet controversial. Further epidemiological research and studies are warranted in order to enhance healthcare planning and cost-effectiveness.

Lumbar spinal disease

Spinal pathology comprises greater than 50% of the neurosurgeon’s workload. Therefore, a comprehensive understanding of spinal pathophysiology is of paramount importance. The spine has three principal biomechanical roles; namely load bearing, mobility, and protection of the neural elements. With obesity on the rise and the ageing population, lumbar spinal disease is set to become increasingly prevalent. This chapter outlines the three key pathophysiological concepts underpinning lumbar spinal disease: spinal function, the motion segment, and spinopelvic balance. In addition, the clinical features pertaining to these common pathological processes are described and the best available evidence guiding treatment is discussed.