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Keywords:

  • Alcock's canal;
  • Colles fracture;
  • cyclopedia;
  • obturator fascia;
  • fascia lunata;
  • ischio-rectal fossa;
  • pudendal

Abstract

  1. Top of page
  2. Abstract
  3. EARLY LIFE AND TRAINING
  4. CAREER AND RESIGNATION
  5. ANATOMICAL CONTRIBUTIONS
  6. CLINICAL SIGNIFICANCES
  7. REFERENCES

Benjamin Alcock (1801–?) was a prominent anatomist from Ireland who is remembered most for his description of the pudendal canal. He was privileged to train under the great Irish anatomist, Abraham Colles. Following his training and several early teaching engagements, he was appointed as the first Professor of Anatomy and Physiology at Queen's College, Cork. He became a Fellow of the Royal College of Surgeons in Ireland. After several years of teaching at Queen's College, Alcock was forced to resign after a dispute over the Anatomy Act of 1832, during which he conveyed his disapproval of participation in the procurement of corpses for the school. Several years after his resignation, he left for the United States and removed himself from the view of the profession. His anatomical contributions were published in The Cyclopaedia of Anatomy and Physiology. The description he gave of the sheath enclosing the pudendal nerve and internal pudendal vessels is his most famous contribution to the literature. He is remembered eponymously for Alcock's canal. This article's intent is to clearly and concisely depict the life and contribution of Benjamin Alcock. Clin. Anat. 26:662–666, 2013. © 2012 Wiley Periodicals, Inc.


EARLY LIFE AND TRAINING

  1. Top of page
  2. Abstract
  3. EARLY LIFE AND TRAINING
  4. CAREER AND RESIGNATION
  5. ANATOMICAL CONTRIBUTIONS
  6. CLINICAL SIGNIFICANCES
  7. REFERENCES

Benjamin Alcock was born in May of 1801 in the town of Kilkenny, Ireland. He was the youngest of five children and came from a rich medical heritage. His father, Nathaniel Alcock, was “a doctor, descended from a long line of doctors” in addition to holding the position of second Mayor of Kilkenny (O'Rahilly, 1947). Benjamin studied at Kilkenny College during his primary education and then took a scholarship in 1819 at Trinity College in Dublin. At Trinity College, he studied anatomy under James Macartney (1762–1813), who was described as “a man of the greatest powers both as an anatomist, a biologist, and surgical teacher” (Trinity College, 1892). Macartney was considered to be the first in Britain to have taught topographical anatomy that emphasized the relationship of structures to one another (Jones, 1950). Because of his reputation, the number to medical students increased greatly during Macartney's time at Trinity (Trinity College, 1892).

While studying at Trinity, Alcock was indentured to Abraham Colles, who served as the Professor of Anatomy and Surgery at Dublin University and was considered to be “the leading Irish surgeon of his time” (Jones, 1950). This unpaid apprenticeship to Colles probably lasted for several years and allowed Alcock to learn from a skilled anatomist and surgeon. Colles endeavored to teach topographical anatomy and published “A Treatise on Surgical Anatomy” in 1811, which was the first publication to place emphasis on this new approach (Jones, 1950). In this study, he discussed the anatomy of the perineum, with particular focus on the superficial fascia, which is a continuation of scarpa's fascia, overlying the urogenital triangle. This fascial layer is better known today as Colles' fascia. In the same year, he also accomplished the first ligation of the subclavian artery in Ireland (O'Rahilly, 1947). A few years later in 1814, he wrote a paper titled “On fracture of the carpal extremity of the radius” (O'Rahilly, 1947). This common injury had hardly been described in the literature before 1814 and many attributed the injury to a dislocation of the carpus. In a time before X-rays, Colles was able to accurately describe the injury as a fracture of the distal radius as well as give a description of the deformity and a method of setting the fracture. As a result of this classical paper Colles was established as a great clinical surgeon and now this injury bears the name Colles' fracture (Jones, 1950). Cameron (1916) reported of Alcock that “under that great master, he became an accomplished anatomist.”

Alcock graduated in 1821 with a B.A. from Trinity College and then several years later, on June 28, 1825, he became a Licentiate of the Royal College of Surgeons in Ireland. He received the degree of M.B. at the University of Dublin in 1827 and later that year, on the 3rd of November, he was elected a Member of the Royal College of Surgeons in Ireland (O'Rahilly, 1947). In 1832, he applied for the Chair of Medicine at the College of Surgeons with seven other applicants but for unknown reasons, failed to obtain the position. Over a decade later, in 1844, a supplemental charter obtained from Queen Victoria divided Members into Licentiate and Fellows. The status of Fellow was granted to those who had graduated at least 3 years previously and who had also taken a licensing examination. Alcock then became a Fellow and gained the degree of M.D. (O'Rahilly, 1947).

CAREER AND RESIGNATION

  1. Top of page
  2. Abstract
  3. EARLY LIFE AND TRAINING
  4. CAREER AND RESIGNATION
  5. ANATOMICAL CONTRIBUTIONS
  6. CLINICAL SIGNIFICANCES
  7. REFERENCES

Alcock began his teaching career in January 1825 at Park Street School in Dublin where he was a Demonstrator of Anatomy and later taught anatomy at the Peter Street School in 1836. In the following year a new school opened, the School of the Apothecaries' Hall on Cecilia Street, where Alcock became Professor of Anatomy, Physiology, and Pathology. He worked at the Apothecaries' Hall for over a decade (O'Rahilly, 1947). In 1849, the Lancet (1849) recorded his new appointment as the first Professor of Anatomy and Physiology at Queen's College, Cork in which it was stated that: “Dr. Benjamin Alcock has been appointed professor of anatomy in Queen's College, Cork, vice Dr. Carte, who has been obliged to retire, in consequence of ill-health.” The medical school at the College opened in November 1849 and started with 20 students. Unfortunately, Alcock was only at Cork for a few years and in 1854 was forced to resign his position (O'Rahilly, 1947).

The reason for Alcock's forced resignation was due to a dispute between him and the schools administration and the procurement of corpses following the passing of the Anatomy Act. As background to this unfortunate event, the Anatomy Act of 1832 legalized the supply of corpses to medical schools. Previously, the Murder Act of 1752 allowed only the corpses of executed murderers to be used for the medical schools' dissections (Smith and Sage, 1994). As more medical schools opened and executions became rare, there was a shortage of fresh cadavers, which lead to a surge in grave robbers who would supply corpses to medical schools for profit. It even became such a lucrative career that some people were murdered for the grave robbers to deliver enough bodies to medical schools. Evidence of this is the trial and hanging of two English men, John Bishop and Thomas Williams, who were convicted of murder with the intent to sell the corpses to London medical schools (MacDonald, 2009). To ameliorate the problem, the intention of the Anatomy Act was to establish an Inspectorate who would oversee the manner in which the schools procured corpses as well as to allow an authorized person to donate a corpse that they lawfully possessed. This especially applied to those in charge of hospitals and workhouses, where large numbers of poor people died (MacDonald, 2009).

The cause for Alcock's resignation stemmed from his disapproval of requests to participate in illegal activities in the procurement of corpses. Like many medical schools after the passing of the Anatomy Act, the anatomy department at Cork experienced a further depletion in its supply of corpses. The Inspector of Anatomy for Ireland, Professor O'Connor, along with Sir John Long, who was held the greatest authority under the Anatomy Act in Ireland, had suggested to Alcock that he “should obtain subjects from the poorhouse by claiming bodies in the capacity of a friend of the deceased” (O'Rahilly, 1948). When Alcock did not go along with the suggestion, the Earl of St. Germans asked for his resignation in December 1853, stating that his remaining in the College “was not beneficial, nor of good example” (O'Rahilly, 1947). Alcock resigned in 1854 but petitioned the Queen, who passed the matter back to the Lord Lieutenant of Ireland. The Lord Lieutenant declined to pursue the matter further since the Earl of St. German had already made a ruling. So in July 1855 Alcock was dismissed. Following his dismissal, Alcock “considered that he was badly treated by the authorities, and published a pamphlet upon the subject of his grievances” (Cameron, 1916). This pamphlet resides in the Library of the Royal College of Surgeons in Ireland. Alcock also recounted his case in the Dublin Medical Press in 1855. In explaining the details of his case, he stated that seven reasons were given for his dismissal, but that five were first communicated to him only by the same letter which contained the demand for his resignation (Alcock, 1855). One of reasons given was that the proposed method of obtaining corpses had been carried out at other schools and should have been satisfactory. Alcock responded, “I did not concur in or adopt the arrangement for supplying subjects, proposed by Professor O'Connor, and urged for adoption in Cork, in the name of the Earl of St. Germans, by Sir John Young, the chief authority under the Anatomy Act in Ireland. That arrangement was illegal. It involved a misdemeanor; and its illegality were admitted even by its proposer” (Alcock, 1855). Even with this account of attempting to follow the law, despite the urges from his superiors, Richardson (2000) stated that he “had broken ranks with his profession, and with the English ruling elite in Ireland, and was never forgiven…He would probably never again have obtained an academic post in his subject in British dominions.” Several years later Cameron (1916) noted of Alcock “in 1859, being then unmarried, he went to America, and has not since been heard of.”

ANATOMICAL CONTRIBUTIONS

  1. Top of page
  2. Abstract
  3. EARLY LIFE AND TRAINING
  4. CAREER AND RESIGNATION
  5. ANATOMICAL CONTRIBUTIONS
  6. CLINICAL SIGNIFICANCES
  7. REFERENCES

Alcock is best known for his description of the course of the pudendal nerve, as it runs through the pudendal canal (Alcock's canal). He described this region of anatomy in his contribution to The Cyclopaedia of Anatomy and Physiology, which was edited by Robert B. Todd and published from 1835 to 1859. However, the Cyclopaedia did not receive praise from all. Macalister (1884) stated that the authors showed “a thorough lack of originality” and the articles “all deal with subjects of common dissecting-room anatomy…except perhaps those of Alcock.” Alcock's contributions were specifically articles on the femoral artery, the “fifth pair of nerves,” the “fourth pair of nerves,” and the “iliac arteries” (O'Rahilly, 1947). Cameron (1916) noted that “his observations on the non-ganglionic portion of the fifth pair of nerves were original; they were confirmed and extended by Guyot and Casales, and reported to the Academy of Medicine, Paris, in 1839.”

The article in the Cyclopaedia dealing with the iliac arteries is where Alcock provided his description of the pudendal canal, where he described it as being “in the obturator fascia” (O'Rahilly, 1947) (Fig. 1). Through this canal, the internal pudendal artery and vein also travel.

image

Figure 1. With permission from O'Rahilly (1947). Extract from original description of Canalis pudendalis in Todd's Cyclopedia (1836–1839, Vol. 2, p. 835).

Download figure to PowerPoint

“In a canal in the obturator fasica the artery [internal pudendal] is contained through the posterior part of the third [perineal] stage; by some it is maintained to be between the fascia and the muscle, in a sort of canal formed internally [medially] by the fascia, externally [laterally] by the muscle and tuberosity, and inferiorly by the great sciatic [sacrotuberous ligament; but this is not correct; the vessel being in the fascia, and not external [lateral] to it; the line of its course is convex downward, about an inch and a half from the under surface of the tuberosity of the ischium at its most depending part, and from two to two and a half inches from the surface, this distance varying of course according to the condition of the subject; the line approaches the margin of the ramus or the spinous process thence forward of backward” (Todd, 1836–1839).

Years later, Derry (1907) discovered an additional fascial layer termed the fascia lunata. He described it as “a very dense crescentic mass of fibrous tissue, which covers in the lowest, most ventral portion of the obturator internus muscle. This structure, which I have called the fascia lunata, is actually that part of the obturator fascia which forms the outer wall of the ischio-rectal fossa, and encloses the pudic vessels and nerve in a sheath usually known as Alcock's canal” (Derry, 1907). A contemporary and contributor to Derry's work was Elliot Smith, a professor of anatomy in Cairo, Egypt who also had written about this structure and stated, “It is not correct to describe Alcock's canal as formed by ‘the splitting of the obturator fascia’. It consists of an investment of fibrous tissue, which has nothing to do with the sheath of the obturator internus muscle, and is attached to the neighboring bony and ligamentous structures quite independently of it. It often happens (in the case of the human pelvis) that the fascia lunata becomes attached to the surface of the sheath of the obturator internus, but this does not always happen” (Smith, 1908). He also noted that, “the term Alcock's canal is usually restricted to that part of the fascia lunata which forms part of the wall of the ischio-rectal fossa but the fascia lunata continues to provide a sheath for the internal pudendal vessels and pudendal nerve even in the urogenital region” (Smith, 1908).

CLINICAL SIGNIFICANCES

  1. Top of page
  2. Abstract
  3. EARLY LIFE AND TRAINING
  4. CAREER AND RESIGNATION
  5. ANATOMICAL CONTRIBUTIONS
  6. CLINICAL SIGNIFICANCES
  7. REFERENCES

Pudendal Neuralgia

Pudendal neuralgia is a painful neuropathy involving the pudendal nerve in its associated distribution. The pain is characterized as a burning, tingling, or numbing pain in the areas of the vulva, vagina, clitoris, the glans penis, scrotum excluding the testicles, perineum, or rectum (Robert et al., 1998; Hibner et al., 2010). Depending on the cause the distribution of the pain can bilateral or unilateral and if affecting the distal branches of the nerve can be restricted to only the clitoris, vulva, vagina, or rectum (Labat et al., 2008; Hibner et al. 2010). In 2008, a publication by Labat et al. listed the “Nantes Criteria” which illustrates five inclusion criteria, eight complementary diagnostic criteria, four exclusion criteria, and nine associated signs for the diagnosis of pudendal neuralgia (Hibner et al., 2010).

Historically pudendal neuralgia has been a synonym for Alcock's canal syndrome or pudendal nerve entrapment. There are many causes of pudendal neuralgia which include mechanical injury, viral infection, or immunologic processes (Campbell and Meyer, 2006; Hibner et al., 2010).The mechanical injury to the pudendal nerve includes entrapment along any portion of its course, including the portion coursing through Alcock's canal thus giving the name “Alcock's canal syndrome,” blunt pelvic trauma or rarely childbirth. The entrapment of the pudendal nerve can be caused by muscle spasms, compression by local structures or scar tissue formation postsurgery (Shafik, 2002; Hibner et al., 2010).

Treatment of pudendal neuralgia is dependent on the etiology. The treatment options include behavior modification, physical therapy, pudendal nerve block, corticosteroid injections, and surgical decompression (Stav et al., 2009).

Alcock's Syndrome or Pudendal Nerve Entrapment

Alcock's canal syndrome or pudendal nerve entrapment is a condition in which the pudendal nerve is compressed resulting in a neuralgia in the distribution of the pudendal nerve. A recent study by Filler et al. in 2009 classified the entrapment into four categories with two subcategories for Type III. The categories are as follows: Type I, entrapment at the level of the piriformis muscle in the sciatic notch; Type II, entrapment at the level of the ischial spine and sacrotuberous ligament; Type III, entrapment in the Alcock canal (Type IIIa entrapment by the obturator internus muscle only, Type IIIb entrapment by the obturator internus and the periformis muscle); and Type IV, entrapment of the distal branches of the pudendal nerve (Filler, 2009). Although Alcock's canal is involved in only one type of pudendal nerve entrapment Alcock's canal syndrome is historically used synonymously with any form of pudendal nerve entrapment. Furthermore, in his description Alcock only mentions in passing that the pudendal nerve courses through the canal and focuses more on the description of the pudenal artery and its course (Colebunders et al., 2011).

In the event that the patient is suspected of a pudendal nerve entrapment diagnostic MIR-guided injections are used to locate the area in which the nerve is compressed. The recommended surgical decompression by resection and neuroplasty of the pudendal nerve vary depending on the location of the compression. In the study conducted by Filler, the recommended surgical options include: Type I, piriformis resection and neuroplasty at the level of the superior (in the sciatic notch) and inferior (as the nerve exits the sciatic notch) retrosciatic spaces; Type II, neuroplasty at the level of the ischial spine with the option of sectioning the sacrotuberous or sacrospinous ligaments; Type IIIa, neuroplasty of the nerve to the obturator internus muscle and the pudendal nerve at the level of the inferior retrosciatic space, lesser sciatic notch and proximal to Alcock's canal; Type IIIb, the same procedure as for Type I with the addition of the procedure for Type IIIa; and Type IV, neuroplasty of the distal pudenal branches (Filler, 2009). There has also been some dispute in the past as to who should be given credit for the name “Alcock's canal.” Several older sources have attributed the naming of the pudendal canal to Thomas Alcock, M.D., who was born in Rothbury, Northumberland in 1784. Although he had written several articles for medical journals, O'Rahilly (1947) wrote of Thomas Alcock that, “he was the author of numerous papers in medical journals he has no claim to be considered as an anatomist” (O'Rahilly, 1947). Dobson (1946) also noted that this ascription to Thomas Alcock was incorrect as Benjamin Alcock was the rightful origin of the description.

Benjamin Alcock served mankind with distinction in a difficult era of medicine. He had the privilege to train under one of the brightest medical minds of his time, while also having the ill fortune of having to answer to unjust and crooked authorities. He lost his position at Queen's College, a role to which he had dedicated his life's training. Today he is remembered for having been a great anatomist, and particularly for his anatomical description of the pudendal canal, which continues to hear his name.

REFERENCES

  1. Top of page
  2. Abstract
  3. EARLY LIFE AND TRAINING
  4. CAREER AND RESIGNATION
  5. ANATOMICAL CONTRIBUTIONS
  6. CLINICAL SIGNIFICANCES
  7. REFERENCES
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  • Derry DE. 1907. On the real nature of the so-called “pelvic fascia.” J Anat Physiol 42:97106.
  • Dobson J. 1946. Anatomical Eponyms. London:Bailliere, Tindall & Cox.
  • Filler AG. 2009. Diagnosis and treatment of pudendal nerve entrapment syndrome subtypes: Imaging, injections, and minimal access surgery. Neurosurg Focus 26:114.
  • Hibner M, Desai N, Robertson LJ, Nour M. 2010. Pudendal neuralgia. J Minim Invasive Gynecol 17:148153.
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  • Labat JJ, Riant T, Robert R, Amarenco G, Lefaucheur JP, Rigaud J. 2008. Diagnostic criteria for pudendal neuralgia by pudendal nerve entrapment (Nantes criteria). Neurourol Urodyn 27:306310.
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  • Macalister A. 1884. A sketch of the history of anatomy in Ireland. Dublin J Med Sci 77:119.
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  • Richardson R. 2000. Death, Dissection, and the Destitute. Chicago, IL:University of Chicago Press.
  • Robert R, Prat-Pradal D, Labat JJ, Bensignor M, Raoul S, Rebai R, Leborgne J. 1998. Anatomic basis of chronic perineal pain: Role of the pudendal nerve. Surg Radiol Anat 20:9398.
  • Shafik A. 2002. Pudendal canal syndrome: A cause of chronic pelvic pain. Urology 60:199.
  • Smith AL, Sage V. (eds.)1994. Gothick Origins and Innovations. Amsterdam:Rodopi.
  • Smith GE. 1908. Studies in the anatomy of the pelvis, with special reference to the fasciae and visceral supports. J Anat Physiol 42:198218.
  • Stav K, Dwyer PL, Roberts L. 2009. Pudendal neuralgia. Fact of fiction? Obstet Gynecol Surv 64:190199.
  • The Book of Trinity College. 1892. The Book of Trinity College, Dublin, 1591–1891. Belfast:Marcus Ward & Co. p108.
  • Todd RB. (ed.)1836–1839. Cyclopaedia of Anatomy and Physiology. London:Longman, Brown, Green, Longmans, & Roberts.