A review of the T2 segment of the brachial plexus.

Although the complex architecture of the brachial plexus (BP) has been described for decades, recent literature still aims to elucidate the variation in nerve root contributions to the BP. Understanding this variability in the nerve morphology of the BP may assist physicians and surgeons in the diagnosis and management of certain clinical conditions that involve the BP, either directly or indirectly due to its close association with neighbouring structures. In this article, we review the current anatomical knowledge of the BP, focusing especially on its T2 contribution, and discuss the causes and consequences of some relevant BP pathologies.

Princeps pollicis artery arising from the superficial palmar arch.

We present a 48-year-old male cadaver in which the right superficial palmar arterial arch had no contribution from the radial artery and terminated by giving rise to a common trunk for the princeps pollicis and radialis indicis arteries. The dorsal radial artery of the thumb was absent and no arterial supply was provided by the radial artery. Accordingly, the entire arterial supply to the right thumb was provided by the superficial palmar arterial arch, which was composed solely of the ulnar artery, which received no collateral supply from the radial artery system. Considering that the arterial supply of the thumb in the present case was solely provided by the superficial palmar arch, a potential hazard could exist in the event of traumatic injury to the ulnar artery.

Morphologic variation of the diaphragmatic crura: a correlation with pathologic processes of the esophageal hiatus?

The contributions of muscle fibers from the right and left diaphragmatic crura to the formation of the esophageal hiatus have been documented in several studies, none coming to a complete consensus on the number of anatomic variations or the prevalence of these variations in the human population. These variations may play a role in the pathogenicity of specific diseases that involve the esophageal hiatus, such as hiatal hernias. We examined a total of two hundred adult cadavers during 2000-2007. The variations in the diaphragmatic crura, particularly their muscular contributions to the formation of the esophageal hiatus, were grossly examined and revealed a bilateral occurrence of diaphragmatic crura in all 200 specimens. The results of the various morphological patterns of circumferential muscle fibers forming the esophageal hiatus were classified into six groups. The most common type (Type I, 45%) formed the esophageal hiatus from muscular contributions arising solely from the right crus. In Type II (20%) the esophageal hiatus was formed by muscular contributions from the right and left crura. In Type III (15%), the right and left muscular contributions arose from the right crus with an additional band from the left crus. Type IV (10%) showed that the right and left muscular contributions arose from the right crus, with two additional (anterior and posterior) bands arising from the left crus. Type V (5%) demonstrated the contributions arising solely from the left crus. In Type VI (5%) the right and left contributions originated from the left crus with two additional bands, one from the right crus and one from the left crus. These variations may play a role in the pathogenicity of specific diseases that involve the esophageal hiatus such as hiatal hernia, gastroesophageal reflux disease and Dunbar's syndrome.

An unusual union of the intercostobrachial nerve and the medial pectoral nerve.

Variations in the branching pattern of the intercostobrachial nerve have been known to complicate dissection during mastectomy and other procedures involving the axilla. We present the case of an 87-year-old Caucasian female, in whom the intercostobrachial nerve joined with a separate branch from the medial pectoral nerve. The clinical consequences of such a variation may include pectoral muscle motor loss, in addition to the commonly reported sensory loss resulting from the accidental injury or intentional sacrifice of the intercostobrachial nerve during axillary dissection.

The first description of the palmaris brevis muscle.

Giovanni Battista Canano was born in Italy in 1515 and his work has gone mostly unknown. Very few copies of this anatomist and physician's book are known to exist. Interestingly, Canano reported and depicted what we believe, to be the first description of the palmaris brevis muscle. This description would be some 200 years prior to what is thought to be the earliest mention of this muscle by William Cheselden in his book, The Anatomy of the Human Body, published in 1713.

The ansa cervicalis revisited.

Recurrent laryngeal nerve paralysis represents a major complication in oesophageal cancer surgery. Nerve-muscle transplantation to the paraglottic space after resection of the recurrent laryngeal nerve with the ansa cervicalis (AC) has recently become the procedure of choice. The aim of this study was to investigate the anatomical variations of AC in order to avoid iatrogenic injuries and facilitate surgical procedures. We examined 100 adult human formalin-fixed cadavers. The ansa cervicalis showed a great degree of variation regarding origin and distribution. The origin of the superior root of AC was found to be superior to the digastric muscle in 92% of the cases. Its vertical descent was found to be superficial to the external carotid artery in 72% and superficial to the internal carotid artery in 28% of the specimens. The inferior root of AC was derived from the primary rami of C2 and C3 in 38%, from C2, C3 and C4 in 10%, from C3 in 40% and from C2 in 12% of the cases. The inferior root passed posterolaterally to the internal jugular vein in 74% and anteromedially in 26% of the cases. The roots of AC were long (70%) or short (30%), and the union between the two roots was situated inferior or superior to the omohyoid. Not only is knowledge of the anatomy of the ansa cervicalis important for nerve grafting procedures, but surgeons should be aware of AC and its relationships to the great vessels of the neck in order to avoid inadvertent injury during surgical procedures of the neck.

The clinical anatomy of the internal thoracic veins.

The branching pattern and adequacy of the internal thoracic veins (ITV) are important factors, providing useful information on the availability of vessels and their appropriateness as an option for anastomoses in plastic and reconstructive surgery. During 100 cadaveric examinations of the anterior thoracic wall it was observed that ITVs were formed by the venae commitantes of ITAs, which united to form a single vein (one for the right side and one for the left) draining into the right and left brachiocephalic veins. The tributaries of ITVs corresponded to the branches of ITA. The right internal thoracic vein bifurcated at the 2(nd) rib in 36% of the specimens, at the 3(rd) rib in 30% of the specimens, at the 4(th) rib in 10% of the specimens and in 24% of the specimens it remained a single vein. The left internal thoracic vein bifurcated at the 3(rd) rib in 52% of specimens, at the 4(th) rib in 20% of specimens and in 28% of the specimens it remained as a single vein. In addition, it was observed that in 78% of specimens ITVs were connected to each other by a venous arch. This arch displayed four distinct morphologies: transverse (n = 7), oblique (n = 16), U-shaped (n = 51) and double-arched (n = 4). All 78 arches were posterior to the xiphisternal joint and no artery accompanied them. In the remaining specimens, RITV and LITV exhibited a venous plexus formation. The distance from the sternum to ITV gradually decreased as the vessel passed caudally; the diameter of the vessel similarly decreased along the vein's caudal course. The frequent appearance of two concomitant veins on both sides of the thorax may offer the opportunity to reduce venous congestion by two vein anastomoses. More detailed knowledge of the anatomy of ITV may prove useful in planning surgical procedures in the anterior thorax in order to avoid unexpected bleeding.

Identification of greater occipital nerve landmarks for the treatment of occipital neuralgia.

Important structures involved in the pathogenesis of occipital headache include the aponeurotic attachments of the trapezius and semispinalis capitis muscles to the occipital bone. The greater occipital nerve (GON) can become entrapped as it passes through these aponeuroses, causing symptoms of occipital neuralgia. The aim of this study was to identify topographic landmarks for accurate identification of GON, which might facilitate its anaesthetic blockade. The course and distribution of GON and its relation to the aponeuroses of the trapezius and semispinalis capitis were examined in 100 formalin-fixed adult cadavers. In addition, the relative position of the nerve on a horizontal line between the external occipital protuberance and the mastoid process, as well as between the mastoid processes was measured. The greater occipital nerve was found bilaterally in all specimens. It was located at a mean distance of 3.8 cm (range 1.5-7.5 cm) lateral to a vertical line through the external occipital protuberance and the spinous processes of the cervical vertebrae 2-7. It was also located approximately 41% of the distance along the intermastoid line (medial to a mastoid process) and 22% of the distance between the external occipital protuberance and the mastoid process. The location of GON for anaesthesia or any other neurosurgical procedure has been established as one thumb's breadth lateral to the external occipital protuberance (2 cm laterally) and approximately at the base of the thumb nail (2 cm inferior). This is the first study proposing the use of landmarks in relation to anthropometric measurements. On the basis of these observations we propose a target zone for local anaesthetic injection that is based on easily identifiable landmarks and suggest that injection at this target point could be of benefit in the relief of occipital neuralgia.

A case of atypical insertion of the levator scapulae.

Anatomical variations in the musculature of the spine have the potential to cause functional and postural abnormalities, which in turn could lead to chronic myofascial and skeletal pain. We present a unilateral case of a 71-year-old Caucasian female in which the left levator scapulae muscle gave rise to an accessory head that inserted, by way of a flat aponeurotic band, to the ligamentum nuchae, the tendon of the rhomboideus major and the superior aspect of the serratus posterior superior muscle. The innervation was provided by a branch of the dorsal scapular nerve. By exerting unilateral traction on the vertebrae and surrounding musculature, this unusual variation might have resulted in clinical consequences including scoliosis and movement abnormalities of the head and neck as well as myofascial pain syndrome.

A retrotracheal right subclavian artery in association with a vertebral artery and thyroidea ima.

The retro-oesophageal right subclavian artery is an anatomical abnormality encountered by anatomists and pathologists and, more recently, interventional cardiologists and thoracic surgeons with an incidence of 0.2-2% in the population. We report a case of a retrotracheal right subclavian artery which originated distally along the left aortic arch and coursed between the trachea and the oesophagus. Additionally, the aortic arch gave rise to a common trunk, which subsequently bifurcated to yield to a right vertebral artery and a left thyroidea ima, replacing the left inferior thyroid artery. Consequently the right and the left recurrent laryngeal nerves were found to recur normally. The possible embryonic development of these branching patterns and their clinical significance is discussed.

Iliolumbar membrane, a newly recognised structure in the back.

Despite intensive research in the anatomical sciences for the last two centuries, some structures of the human body still remain controversial or incompletely described. We describe a new membranous fascial anatomical entity, which we refer to as the iliolumbar membrane (ILM). During the 2004-2005 academic semesters at the American University of the Caribbean School of Medicine we dissected 40 human cadavers fixed in formalin-alcohol-phenol solution. Iliolumbar membrane is a thick connective tissue structure, deep to the skin, originating from the fibres of the thoracolumbar fascia at the lateral border of the erector spinae. It runs inferior to the superior border of the iliac crest, lateral to the posterior superior iliac spine, overlying the iliac crest at the level of the 4th lumbar vertebra. Iliolumbar membrane terminates within subcutaneous fat, where it divides into multiple layers. All cadavers showed considerable variation in the blending of the membrane's multiple layers with the subcutaneous fat. However, all specimens consistently showed a uniform appearance of ILM at the point of origin. Iliolumbar membrane could be demonstrated objectively by ultrasound examination with a frequency of 7.5 MHz and also with a Stryker endoscope. A hypothesis is put forth, conjecturing that this new structure may have relevance in creating a natural barrier between the musculature of the back and the muscles of the gluteal region, similar to Scarpa's fascia of the anterior abdominal wall.

A case of an anomalous pectoralis major muscle.

We present a case of a right sided accessory head of the pectoralis major muscle located inferior to its abdominal head. This variation was found during a routine anatomy dissection at the American University of the Caribbean School of Medicine. The muscle fibres of the accessory head of the pectoralis major muscle arose from those of the serratus anterior muscle and travelled superolaterally towards the axilla. The accessory muscle terminated by fusing with the tendinous fibres of the pectoralis major muscle as they underwent their normal anatomical rotation before insertion upon the lateral lip of the bicipital groove of the humerus. Although variations in the pectoral muscles are not uncommon, this case appears to be unique in the literature. The possible clinical implications are discussed.