Nerve Surgery (eBook)

Susan E. Mackinnon (Autor)

eBook Download: EPUB

2015 | 1. Auflage
646 Seiten
Georg Thieme Verlag KG
978-1-63853-013-8 (ISBN)

Infos

<p>Representing the treatment and management philosophy of Dr. Susan Mackinnon, Nerve Surgery provides extensive coverage of innovative surgical options as well as guidance on the management of complicated compression neuropathies. In addition to detailed information on tried-and-true as well as cutting-edge surgical techniques, it contains chapters on the basic principles of nerve surgery, such as 'Anatomy and Physiology for the Peripheral Nerve Surgeon' and 'Evaluation of the Patient with Nerve Injury or Nerve Compression.'</p><p>Key Features:</p><ul><li>More than 850 compelling full-color figures and photographs demonstrate key concepts</li><li>Videos narrated by Dr. Mackinnon are available online</li><li>Coverage of important conditions that can be treated non-operatively, such as neurogenic thoracic outlet syndrome and multilevel compression neuropathy</li><li>Strategies and secondary procedures for failed nerve surgeries</li><li>Dr. Mackinnon provides tips on how she manages complicated pain problems</li></ul><p>This book is a core reference for all plastic surgeons, neurosurgeons, orthopedic surgeons, hand surgeons, residents, and allied health specialists treating patients with nerve injuries.</p>

Textauszug

1 Anatomy and Physiology for the Peripheral Nerve Surgeon

Matthew D. Wood, Philip J. Johnson, and Terence M. Myckatyn

1.1 Introduction

At a macroscopic level, peripheral nerve anatomy has been extensively studied and documented, and our understanding of the fascicular arrangements of specific nerves has evolved with the development of nerve transfers. Our understanding of nerve anatomy and physiology at the subcellular level has grown at a remarkable rate and offers new insights into the mechanisms of neurodegeneration, regeneration, and novel therapeutic targets to manipulate.

1.2 Nerve Fiber Anatomy

Uninjured peripheral nerves are composed of unmyelinated or myelinated mature axons (▶ Fig. 1.1) that are opposed by Schwann cells.

Fig. 1.1 Peripheral nerve: morphology. (a) The normal peripheral nerve is composed of neural tissue and connective tissue components. The nerve fibers may be myelinated or unmyelinated. (b) A population of myelinated and unmyelinated nerve fibers are seen. The basement membrane of the Schwann cell is a double basement membrane (arrow) that can only be identified by electron microscopy. A, axon; C, endoneurial collagen; M, myelin; NR, node of Ranvier; SCN, Schwann cell nucleus; ua, unmyelinated axon (uranyl acetate, 4750x).

Several unmyelinated axons are surrounded by one Schwann cell–derived double basement membrane, whereas myelinated axons are ensheathed by laminin-rich, multilaminated sheets of myelin (provided by a single Schwann cell). Individual axons are immediately surrounded by thin collagen fibers forming an endoneurium and are further sorted into fascicles defined by a discrete connective tissue sheath known as the perineurium. Between these fascicles is the internal epineurium. A thicker, connective tissue sheath termed the external epineurium encompasses all the fascicles that group together to form a single nerve. Nerves accommodate shortening and lengthening during flexion and extension of an extremity by being bounded by the epineurium and delimited by areolar connective tissue, the mesoneurium, interspersed with a protective fatty tissue cocoon. When the full range of motion of an extremity is compromised, patients are more at risk for traction and compression neuropathies (▶ Fig. 1.2). This is becoming more common as our population becomes on average more obese, more deconditioned, and older.

Fig. 1.2 Peripheral nerve axon: anatomical organization. Axons are either myelinated or unmyelinated and are shown here as the small (yellow) fibers to the right. Myelinated axons are associated with a single Schwann cell, whereas unmyelinated axons are small, and multiple axons can be associated with one Schwann cell. Individual axons are immediately surrounded by thin collagen fibers forming an endoneurium and are further sorted into fascicles defined by a discrete connective tissue sheath known as the perineurium (green). Between these fascicles is the internal epineurium (dark yellow). A thicker connective tissue sheath, the external epineurium, encompasses all the fascicles that group together to form a single nerve. Nerves accommodate shortening and lengthening during flexion and extension of an extremity by being bounded by the epineurium and delimited by areolar connective tissue, the mesoneurium, interspersed with a protective fatty tissue cocoon.

(Used with permission from Mackinnon SE, Dellon AL, eds. Surgery of the Peripheral Nerve. New York, NY: Thieme; 1988:21.)

1.2.1 Fascicular Anatomy

Nerves in the proximal extremity are monofascicular, but even at this level, motor and sensory fibers are grouped together topographically. There is considerable plexus formation between the fascicles in the proximal portion of the extremity that decreases in the distal extremity. As nerves progress distally, they become polyfascicular, but fascicles are differentiated into specific motor and sensory components even in proximal locations.1,2,3 In the proximal segment of the nerve, motor versus sensory fibers are distinguished by knowledge of the internal topography, which has come predominantly from intraoperative stimulation of normal nerves to identify motor and sensory topography.3,6 Using intraoperative stimulation techniques, we have seen a very specific motor response to stimulation of a single teased fasicle.

Knowledge of the usual internal topography of the peripheral nerves can direct proper alignment of fascicles at the time of nerve repair to optimize the specificity of modality- and function-matched reinnervation. For example, the fascicles of the ulnar nerve in the mid- and distal forearm are divided into a dorsal sensory group, a volar sensory group, and a motor group (▶ Fig. 1.3). In the mid-forearm, the motor group is positioned between the ulnar dorsal sensory group and the radial volar sensory group. The dorsal sensory group separates from the main ulnar nerve ~ 8 cm proximal to the wrist. The motor group remains ulnar to the volar sensory group until reaching the Guyon canal, at which time it passes dorsal and radial to become the deep motor branch to the intrinsic muscles. The size match between the motor and sensory groups of the main ulnar nerve at this level is ~ 2:3.

Fig. 1.3 Internal topographical anatomy of the ulnar nerve. The ulnar nerve has a distinct fascicular pattern as it courses distally from the forearm into the hand. The motor component of the ulnar nerve is found between the sensory component and the dorsal cutaneous fascicles. Distal to the dorsal cutaneous nerve branch point, the motor component is identified on the medial aspect of the ulnar nerve. This motor component branches from the ulnar nerve on its medial/ulnar aspect to become the deep motor branch, then dives deep to the leading edge of the hypothenar muscles to course around the hook of the hamate and innervate the intrinsic muscles. The sensory component of the ulnar nerve is a larger fascicular group than the motor component and innervates the ulnar aspect of the ring finger, the small finger, and the fourth web space.

The median nerve topography is more complex because it contains more fascicles (▶ Fig. 1.4). In the forearm, the anterior interosseous nerve is situated in the radial or posterior aspect of the median nerve as a distinct group. The distal internal topography of the median nerve approximates the distal anatomy; the motor fascicles to the thenar muscles are on the radial side, and the sensory fibers to the third web space are on the ulnar side.

Fig. 1.4 Internal topographical anatomy of the median nerve. Proximal forearm: The median nerve is composed of several motor and sensory fascicles. In the proximal forearm, the pronator teres fascicle is on the most anterior aspect, followed medially by the flexor carpi radialis (FCR) and palmaris longus (PL) fascicles. Further medially, the flexor digitorum superficialis (FDS) fascicular group is identified. This fascicular group usually includes two fascicles that correspond to two branch points to the FDS. The anterior interosseous fascicle is on the posterior aspect of the ulnar nerve and continues distally to become lateral/radial before its branch point. This fascicle includes a small sensory articular component to the wrist joint. It is important to acknowledge a thenar motor component within the sensory component. Distal forearm: The anterior interosseous nerve includes three fascicles: flexor pollicis longus (FPL), flexor digitorum profundus (FDP), and pronator quadratus (PQ)/articular. The FPL and FDP fascicles are large compared to the PQ fascicle and have an anterior orientation. The median nerve includes a recurrent thenar fascicle that is found posterior and lateral. As the median nerve courses distally, the sensory fascicles are revealed to have three major groups: first web space and radial aspect of thumb, second web space, and third web space. These groups have a lateral, middle, and medial orientation, respectively. The palmar cutaneous nerve branches from the anterior and lateral aspect of the median nerve. Hand: The recurrent thenar nerve branches from the...

Produkt-Details

• Erscheint lt. Verlag: 15.4.2015
• Sprache: englisch
• Themenwelt: Medizinische Fachgebiete ► Chirurgie ► Neurochirurgie
• Themenwelt: Medizin / Pharmazie ► Medizinische Fachgebiete ► Orthopädie
• Schlagworte: hand surgery • Motor function • nerves • Nerve Surgery • Neural function • neurosurgery • orthopaedic surgery • Peripheral Nerve • Plastic Surgery • Reconstructive Surgery
• ISBN-10: 1-63853-013-0 / 1638530130
• ISBN-13: 978-1-63853-013-8 / 9781638530138