Cranial sutures.

Cranial sutures are not of great concern to the modern neurosurgeon, except when abnormalities interfere with the skull's shape and its ability to expand during childhood. It is a commonplace that a craniotomy may cross a variety of sutures without providing any extra difficulty to the operator. The sagittal suture does remain useful as a definition of the midline of the cranium and as an indicator of the underlying sinus. Galen for reasons that are far from clear, "observed" relationships between the sutures, the meninges and the pericranium which led him to advise avoidance of any surgical proximity to the sutures. The result of this proscription was a severe limit of the access surgeons considered was appropriate and thus limited their ability to care for their patients.

The enlightenment.

The period begins with the work of Richard Wiseman who was associated with royalists in the English Civil War. A little later Dionis was the first to note a relationship between a disturbance of consciousness and extravasation of blood. This notion was continued and expanded by Le Dran, Pott, and Benjamin Bell, with Pott providing a pathophysiological explanation of the phenomenon. Daniel Turner commented on how confusing Galenic teaching was on the topic of consciousness. Heister further emphasized the relationship between clinical disturbance and the extravasation of blood. Le Dran stated that symptoms following cranial trauma related to cerebral injury, an opinion supported by Pott and never subsequently challenged. Latta noted the importance of meningeal arteries in the development of hematomas. Benjamin Bell considered trepanation only appropriate for a clinical deterioration consistent with hemorrhagic extravasation. The two Irish surgeons made it clear that the presence of periosteal separation was not in fact a reliable indicator of an extravasation. The most striking change of instruments was disappearance of simple straight trepans with non-perforating tips for making small holes safely. The use of scrapers gradually declined as did that of lenticulars. There was a great debate about the value of a conical rather than a cylindrical crown. The former was said to be safer. But this opinion faded and the cylindrical crown became preferred. Another improvement in technique involved the use of constant probing to check the depth of the drilled groove.

The Reformation.

The most important text at the end of the Middle Ages was the Bible. It had been published in manuscript on parchment bound between wooden covers. The production of such a book was time consuming and expensive. Martin Luther's proclamation of 95 theses directed against the practice and authority of the Roman Catholic church led to a speedy opposition from the church. However, the modern availability of paper and printing together with the printing of images, resulted in a rapid distribution of the bible in German. The church authorities had banned the spreading of literacy outside the clergy, but the publishing of Luther's bible involved the use of techniques which could be applied to other disciplines, improving the quality of the information on which their activities was based. This included the practice of surgery.

Two surgical instruments.

The only instruments for opening the cranium considered in this chapter are drills, and in some cases facilitated with a special chisel called a lenticular. There were two kinds of trepan. The modiolus was the Latin name for a crown trepan which had a circular base with teeth which sawed a hole. Then there were the non-penetrating trepans which had a bit shaped to prevent unwanted penetration. They made small openings which could be joined by chisels to remove altogether larger areas of bone than were accessible to modioli. They were the favored instrument from the ancient world up to the Renaissance. At the beginning of the Renaissance, there was a move toward greater use of crown trepans and various methods were applied to stop them sinking too far inward. These included wings in the outer wall and changing the shape of the bit from cylindrical to conic. In time preferences returned to the cylindrical shape and larger diameters. There was also two instruments called lenticulars, the illustrations of which have been confused in the literature. It is now clear that the Roman instrument was shaped to cut the cranium and minimize the need for trepanation. The Renaissance instrument had a different shape and was used to smooth rough bone edges and excise spicules penetrating the meninges. They were simply two different instruments to which the same name was applied.

Renaissance-Europe-17th Century.

The authors of the texts described in this chapter will have had access to the anatomy of Vesalius; a marked step forward. However, there was no equivalent advance in physiology. Harvey's book on the circulation of the blood was published in 1628 but it took many years for its contents to be accepted as standard teaching. The century saw the development of instruments some of which look more like instruments a modern surgeon would recognize. The two major technical advances were the acceptance of a single-handed trephine and the design of crown trepans with a conical shape and blades extending up the sides. Moreover, the crown trepan had once again become the favored instrument for gaining access to the interior of the cranium. In terms of technique there was a worrying trend that surgeons could feel when they had penetrated the inner table of the skull without the need to probe. All the way back to Hippocrates, it had been customary to use probes to assess depth while trepanning. Thus, the abandonment of this safety measure if it was real, is cause for concern. However, it is not impossible that probing was continued and simply not mentioned as it was so obviously necessary as not to require comment. The lenticular illustrated remains of the triangular shape first illustrated by Vidius. It is important to note that it was not used to incise the skull but to smooth of rough edges and spicules.

Renaissance-Europe-16th century.

Realistic images became available for the first time. The first major figure was Berengario da Carpi (1460-1530). He made contributions to knowledge. He stated the dura was attached all over the interior of the cranium not just at the sutures. He also noted that deterioration following traumatic hematomas was speedier the deeper within the brain the bleed had occurred and he noticed that post-traumatic neurological deficits were contralateral. Moreover, he introduced new instruments of a practical design. Specifically, he launched trepanation using a brace and bit handle. This instrument required two hands and rotated the trepan in the same direction all the time. In addition, he illustrated a crown trepan in which the bits could be interchanged. He also developed an improved elevator. He also provided the first drawing of a lenticular. The next illustrations came from Vidus Vidius (1509-1569). The illustrations in his text were elegant and realistic but some of them were impractical or unusable. Ambroise Paré (1510-1590) was a major surgeon. He designed an improved brace and bit trepan with a collar to control penetration. He also introduced instruments for expanding a cranial opening by biting up the bone and for depressing the dura to enable material to escape more easily.

The meninges.

The dura was first described in ancient Egypt. Hippocrates insisted that it should be protected and not penetrated. Celsus proposed an association between clinical findings and meningeal damage. Galen proposed that the dura was attached only at the sutures, and he was the first to describe the pia in humans. In the Middle Ages, new interest in the management of meningeal injuries arose, with renewed interest in relating clinical changes to intracranial injuries. These associations were neither consistent nor accurate. The Renaissance brought little change. It was in the 18th century that it became clear that the indication for opening the cranium following trauma was to relieve pressure from hematomas. Moreover, the important clinical findings on which to base an indication for intervention were changes in the level of consciousness.

The pericranium.

The purpose of this chapter is to present how past surgeons have viewed the pericranium and how they have reacted to its appearances. In ancient times, the membrane was considered formed by the dura through the sutures and it retained a relationship with the dura via vessels in the sutures. It was considered advisable to strip it totally from any area to be examined for fissure fractures and also for any area to be trepanned, as pericranial injury was thought to lead to fever and inflammation. In the 18th century, a new idea arose that posttraumatic spontaneous separation of the pericranium from the bone was a reliable indicator of the development of intracranial suppuration. This idea was subsequently refuted. For over two millennia, the pericranium was considered to be an important membrane requiring the close attention of the surgeon. It is no longer required to receive more than minimal attention.

Renaissance-Europe-16th Century continued.

This chapter is limited to the text of Della Cruce, which contains the most comprehensive account of the instruments used in cranial surgery at the time. Of particular importance is Della Cruce's attitude to what he called non-perforating straight trepans, which in general he disliked. It may be noted that his text was the last to describe this sort of instrument. In the succeeding centuries, changes to penetrating instruments were all variations on the shape of different kinds of crown trepan. Like Berengario, Della Cruce described brace and bit trepans with interchangeable bits. Various methods were employed to prevent them penetrating too deeply.

Overview.

The chapter begins with also an outline of the characteristics of four surgeons who changed the direction of thinking and hence of practice. This is followed by a review of the changing ideas which governed surgical practice. Chapter "Two surgical instruments" by Jeremy C. Ganz has examined the uses of drills and lenticulars. In this chapter there is an appraisal of the other instruments used during cranial surgery and how their use related to changing ideas. Finally, there is a concluding section which ties all these elements together.

Evolution of understanding.

From the time of Hippocrates to the early 19th century, knowledge advanced but that was an uneven process. Anatomy was basically defined by Galen and remained cast in stone until the early 16th century. Neuroanatomy was described by Galen but had little practical value, as brain surgery was not possible. The anatomy of the cranium was known and was largely correct. Care was taken to avoid the frontal air sinuses and the venous sinuses and the temporal region. The role of the brain in consciousness was not understood. It was considered the seat of the soul but there was a lack of understanding that damage to it could induce clinical symptoms such as stupor or paralysis. These were variously attributed to injuries to the meninges or the bone. This error was finally corrected in the 18th century when the brain was identified as responsible for much of the clinical disturbance following cranial trauma. All awareness that post traumatic neurological deficit was contralateral was ignored until the late 18th century, although several authors noted it. Likewise, the presence of CSF had to wait until the 18th century until it was recognized. Fissures were treated with trepanation, because of a perceived risk of infection developing between the bone and the dura. Depressed fracture fragments were elevated, replaced, or removed according to the details of the injury. Finally, for centuries surgeons blocked patients ears to reduce the sound of drilling, despite the fact that such a blocking would amplify the noise.

Emigration of Greek Knowledge to the Arab World.

The period described in this chapter reflects activity prior to the establishment of surgical centers in Europe in the twelfth century. It is a kind of prologue to the reintroduction of high-quality surgical practice. Religious squabbles within Christianity led to European medicine and surgery, the principles of which were written in Greek, being transported eastwards into the region newly dominated by Islam. There the works were translated into Arabic and during three to four hundred years, the works were not only retained but were enriched by contributions from within Arab culture. This evolution naturally enough came to affect what happened next. However, one thing is clear and was even commented on as early as by Albucasis. The surgeon's respect and distinction within society had depreciated during the sojourn of medical science in the Islamic world, with physicians being regarded as distinctly superior beings. With regard to specific details related to opening the head there was broad consistency between the various authors all of whom seem to have been greatly influenced by Paul of Ægina. Thus, there is no mention of the crown trepan. Opening the skull was performed with the non-perforating trepans making small holes which were connected with chisels or lenticulars. The indication to do this was separation of the dura from the bone. Whether or not the sutures should be avoided when trepanning is not a topic mentioned in these writings. There was also no recommendation for prophylactic trepanation.

Late Middle Ages-Europe.

At the end of the late Middle Ages, there had been changes in indications for surgery, with prophylactic trepanation falling out of favor. The management of wounds and the methods for opening the cranium had become fairly standardized. Narrow non-plunging trepans were the preferred drills, and cranial openings were widened by the use of multiple drill holes connected with chisels of which the lenticular was preferred. Concerns about damaging the dura led Theodoric to delay trepanation until the clinical changes reflected separation of the dura from the cranium, at least in his view. Draining pus remained the main indication for trepanation. In no case was the level of consciousness considered in determining the need to open the cranium.

Basic considerations.

The chapter reviews certain topics in outline. It starts with a brief account of the nature of surgery. This is followed by a short account of modern management of cranial trauma including the evolution of notions of anatomy and pathophysiology. It is emphasized that these principles are and must be irrelevant to the management of cranial trauma in the period covered in this book from Hippocrates to the end of the 18th century. Historical errors arising from assuming modern principles applied in historical practice are mentioned. Finally, the risks inherent in accepting images without questioning their authorship and provenance is also mentioned.

Trepanation technique.

The larger part of this chapter is concerned with the technique of drilling the cranium with a circular saw called a trepan or trephine. The terminology of the instrument is outlined. Safe use of the instrument includes probing the groove produced by its use and angling the drill so that it impinges on bone which hitherto has not been sawn through. There is then an account of how larger openings may be made by drilling multiple small holes and connecting them by means of a chisel.

Hippocrates (ca 460 BC to ca 370 BC).

The chapter begins with a review of some of the background thinking during Hippocrates time. The brain was considered to be the location of the soul which was the essence of subjective experience. However, this was not a brain function as such but rather a location where the pneuma reacted with the soul. Hippocrates' monograph on cranial trauma begins with a description of the bones and sutures. He then systematized the classification of cranial injury. He sensibly advised accurate diagnosis into one of the types of injury he described and supported extension of any skin opening to facilitate diagnosis of the bone, the injury of which was his primary concern. His description of operative technique has rarely been surpassed, placing emphasis on care and methods for the avoidance of further injury. He also emphasized the importance of probing during trepanation to avoid damaging the dura and underlying brain. In addition, he insisted on using water to cool the trepan. All of this was positive. However, the respect in which he was held in subsequent generations meant that two albeit understandable errors were perpetuated. The first error was the use of prophylactic trepanation to permit the drainage of the pus which he believed would inevitably develop under a fissure. The second was to avoid trepanning at sutures, the reasons for which proscription are not clearly stated. In conclusion, it may be noted that what limited reporting of results is available demonstrates that Hippocrates trepanations were largely not successful.

Rome-Galen (129 to ca. 216).

Over the last 50 years the significance of Galen's contributions to the arts of medicine and surgery have been increasingly recognized. Despite his errors, his contributions to medical and surgical practice have been profound. In the present context, his teachings on cranial surgical instruments and technique would continue to be influential throughout one and a half millenia. His technical advice was sound. His error about the anatomy of blood vessels supplying CNS were not of much consequence since the CNS would remain surgically inaccessible until the end of the 19th century. He reclassified fractures as extending to the diploe or through the internal table. Moreover, they could be simple, comminuted, depressed, or elevated. He did not mention indications or clinical changes, on the other hand he had many sensible remarks to make on the instrumentation required for cranial surgery. As will be seen in what follows, he was much quoted in justification of the decisions of his successors. The major errors of significance related to his description of the anatomy of the cranium and its sutures. His concern about the cranial attachment, vascular components and excretory functions of the sutures added to Hippocrates' concerns about their inherent weakness resulted in the teaching that trepanation should avoid these structures. This was to have a limiting effect on the placement of trepanation openings which was of no benefit to the patients. Moreover, his enthusiasm for bloodletting would also serve to potentiate Hippocrates teaching on this matter, to the advantage of nobody.

Europe following Galen.

Unlike previous chapters, this is not about the teachings of a specific individual. Rather, it traces the slow changes in milieu and practice in the centuries following the death of Galen. They were to be profound. The Roman Empire fell in the middle of the 5th century. The Christian religion became increasingly dominant in the west, not only in spiritual matters but also in every activity related to culture and learning. The Byzantine Empire became increasingly important in the east. Islam was founded and began to spread in competition with Christianity. Academic advances develop best in stable societies so that it is not surprising that this was not a period of new ideas. Galen had gained overwhelming authority. The most valuable work on surgery to be written during these times was Book VI of Paul of Ægina's encyclopedia.

Prehistoric or current primitive cranial operations.

Humankind demonstrates boundless curiosity, mostly expressed through the activities of a small number of individuals, whose achievements affect all members of society. The extent and distribution of pre-historic trepanation and trepanation in contemporary unsophisticated societies are reviewed. In the great majority of cases the intention of trepanation has been therapeutic, even if the understanding of underlying pathophysiology is not the same as that which scientific societies now accept. This review demonstrates variation in surgical technique. In the Atlas Mountains it was unacceptable to operate on the cranial sutures whereas in New Ireland it was not important. Pain relief was unnecessary in Melanesia because the patients were largely unconscious following injury. In South America, there was access to the coca leaf which could help with pain relief. In East Africa, one patient described the application of a powder to his wound which was thought to be for pain relief. The nature of the powder remains unknown. There were differences in the indications for trepanation. In New Britain, the operation was performed only for cases of fracture. In nearby New Ireland, epilepsy and certain forms of mental disturbance were also indications. In North and East Africa, the indication was most frequently headache following trauma. Most of these trepanations did not involve drilling, which is the main subject of this book.

Outside Europe.

This chapter illustrates that cranial surgery was not limited to Europe. There was however no contribution to improving knowledge outside Europe until medical science departed for the Arab world.