International Journal of Osteoarchaeology, vol. 6: 249-258 (1996)

Imaging Evaluation of Skull Trepanation Using Radiography and CT NANCY CHEGE,~ DAVID J. SARTORIS: ROSE TYSON~ AND DONALD RESNICK4

CA 92103-8756, USA; 3San Diego Museum of Man, San Diego, CA, USA; and 4VA. Medical Center, La Jolla, CA, USA

Cupertino, CA, USA; 2UCSD Medical Center, 350 Dickinson Street, San Diego,

ABSTRACT Cranial surgery as practised by the prehistoric and present-day traditional medicine man is the oldest known and one of the highest surgical achievements in the history of medicine. This study examines morbidity and mortality of this ancient surgical procedure by re-examining and reviewing reports of 71 completely trepanned skulls from pre-Columbian Peru by three techniques: gross visual observation and palpation; radiography; and CT. The specimens are located in the San Diego Museum of Man and are part of the Hrdlicka collection. Clear distinction can be made by visual observation between skulls with bone regeneration and those without; that is, between patients who survived long enough to allow bone healing and those who died immediately or within a few days of the operation. 64.8 per cent of skulls had complete healing, 12.7 per cent had partial healing and 22.5 per cent had no evidence of healing. Thus, a post-operative survival rate of 77.5 per cent is noted by gross examination. The meaning of completely trepanned skulls with no evidence of healing is questionable, however, some unhealed skulls may represent post-mortem trepanation, suggesting a lower surgical mortality. Both radiography and CT scan demonstrate with considerable accuracy the presence or absence of new bone formation on trepanned skulls. One skull demonstrated evidence of partial bone healing by CT and radiography but not by our gross examination or by that of some anthropologists. Evidence of osteomyelitis was illustrated by CT scan but not by radiography.

Key words: trepanation; radiography; CT; Peru.

Introduction

Sir William Osler noted on the subject of the origin of medicine, 'Medicine arose out of the primal sympathy of Man with Man; out of the desire to help those in sorrow, need and sickness'.' Indeed, the origin of the present-day neurosurgical procedure of decompression dates back to the neolithic period.'r2 The cranial surgely referred to as trepanation (trephination) is the oldest known therapeutic procedure, as shown by collections of prehistoric skulls in museums world-wide. Indications for trepana- tion as well as surgical survival rate in pre- Columbian Peru remain mostly conjectural and we thought it would be of interest to reconsider possible reasons for trepanation and the surgical morbidity and mortality, not only by gross

obselvation but also by radiography and CT. Skull fractures or depressions at the site of trepanation could suggest trauma as the reason for surgery, whereas pathological conditions such as hyperostosis would suggest intracranial trauma as the reason for ~ u r g e r y . ~ In the pre-Columbian era, surgical morbidity and mortality is evaluated by examination of skulls for normal complete bone healing, partial healing, and no healing.

Prehistorically, trepanation was practised world-wide (with a few exceptions). In the nineteenth and twentieth centuries trepanation has been carried out in Europe, Asia, Africa, Pacific Islands and A r n e r i ~ a . ~ - ~ Literature on the subject of trepanation is extensive, but contro- versy exists on prehistoric motives and techniques. The prehistoric procedure consisted of perforation of the cranium by various

Received 2 August 19 95 Accepted 1 September 1995

ccc l047-482~96/030249-10 0 1996 by John Wiley LQ Sons, Ltd.

2 50 N. Cbege et al.

techniques. Instruments used (called trephine or trepan, which are derived from the Greek word ttypanon, meaning a drill) included hand drills and obsidian flakes. Archaeological evidence as well as the San Diego Museum of Man's collection of skulls suggest four basic techniques: cutting four straight cuts at right angles (tic-tac-toe style) to remove a rectangular piece of bone; scraping with a rough or abrasive stone until the dura is exposed; grooving with a sharp stone point to curve a circular piece of bone from the skull, and drilling a circle of holes with a sharp object followed by cutting the space between the holes to allow removal of a disc of bone-a more dangerous method and therefore probably a rare technique. At present with the addition of general anaesthesia, antibiotics, precision instruments, and sterile operating rooms, surgeons use some of the same techniques as their forerunners but the indications for surgery are almost certainly different.

The first trepanned skull (the Cuzco skull) was discovered in the mid-1800s by an American diplomat, E. G. Squire, who sent it to Paul Broca for further analysis. Since then controversy over the motives for surgery has existed. The sug- gested prehistoric motives for surgery are: therapeutic, to relieve pain or intracranial pressure following head trauma; magical therapy to let out evil spirits; and ritual acts to appease the gods. In neolithic Europe, some operations were per- formed on the dead, either to secure bone amulets (roundels) or possibly to practise surgical techniques. Some degree of healing in a trepanned skull serves as evidence that the operation was performed on a living person.

This stone-age operation on the skull is still practised today (although rarely) in several places of the world. In Kenya, the Kisii tribe is probably the only tribe performing these operations. In the past, a few western physicians have visited the Kisii tribe and have observed the Omobari Omotwe (traditional craniotomist) at his ~ o r k . ~ - ' ~ For the Kisii, motives for surgery are purely therapeuticg or diagnostic and therapeu- tic. ' , I 2 Absolute indications for craniotomy appear to be acute head trauma, where the surgical goal is to remove skull fractures that may be impinging on the brain or to relieve intracranial pressure caused by a subdural haematoma.9

Perhaps the more common elective procedures are indicated for post-traumatic chronic head- aches. It seems that when a Kisii complains of a headache, the condition must be severe given that the craniotomy itself is done under no anaesthesia and that a single patient may undergo multiple craniotomies;9,1° the mortality rate has been reported to be less than 1 per cent.g

Materials and methods

In this study 71 skulls with complete trepanation (both inner and outer tables) from pre-Columbian Peru in the San Diego Museum of Man were examined and published reports reviewed. Specimens were collected from burial sites of the pre-Columbian Incas by Hrdlicka in 1913 and are fully described in the Catalogue of the Hrdlicka Paleopathology Collection.13 Examination of the skulls was carried out using three techniques: gross observation and palpa- tion; radiography; and CT scan. Following a literature review and observation and palpation of all 71 skulls, 1 1 were selected for radiography and of these 9 were selected for CT scan. CT images were made across the longer width of a trepana- tion area and two-dimensional slices of 5 mm and 10mm were cut for small and large defects, respectively. The skulls selected for radiography and CT scan showed normal healing, partial healing, and unhealed skulls based on published reports and on our gross examination. Normal bone healing after surgery is seen at the margins of trepanation openings and is marked grossly by a closing or closed diploe, smooth incisional margins, and to presence of occasional osteo- phytes or bone s p i c ~ l e s . ~ , ~ , ~ ~ , ' ~ Partial or early healing is based on the appearance of new bone without complete closing of diploe, smooth incisional edges or the presence of osteophytes. Normal complete bone healing indicates several years of survival after surgery, because it takes that long for signs of bone regeneration to appear.6 Healing complicated by haemorrhage or infection is marked macroscopically by sub- pericranial bone regeneration with bone resorption.6 Healing with extensive boney no- dules and depressions may suggest healing complicated by osteomyelitis. l 6 Radiologically,

Evaluation of Skull Trepanation

newly formed bone appears more transparent than surrounding bone.6 In addition to signs of thinner (more radiolucent) bone, we looked for bone with less mature architecture (trabecular appears less organized) as well as the more irregular margins of the trepanation defect compared with the sharp borders of a fresh cut. All three signs of healing apply to both radio- graphy and CT scan. Radiographic and CT signs of severe osteomyelitis include osteolysis of the cortex (consequently more radiolucent) and sequestration.” In addition, thickening in new bone suggests that healing may have been complicated by osteomyelitis.

Data were tabulated for the 11 skulls according to the degree of healing. Additional data tabulated includes evidence of fracture (or skull injury), pathology on trepanation area (signs of inflammation, infection, or hyperostosis), and size(s) of trepanation and the resulting aperture(s) (unhealed opening(s) ). Post-operative survival based on the presence or absence of evidence of healing, determined by gross examination was calculated for all 71 skulls. Pathology (osteomyelitis, periostitis, hyperostosis) or

25 1

traumatic injury to the skull was evaluated by all three techniques in an attempt to elucidate possible indications for surgery. Results obtained by radiography and CT scan were compared with those obtained by gross examination.

Table 1. Summary of data for 71 skulls: observatiodpalpation and published r e ~ 0 r t . l ~

Specimens Males Females (per cent) (per cent) (per cent)

Completely healed 46 (64.8) 30 (73.2) 16 (53.3) Partially healed 9 (12.7) 4 (9.7) 5 (16.7) Unhealed 16 (22.5) 7 (17.1) 9 (30.0) Total number of skulls 71 (100) 41 (100) 30 (100)

Survival rate her cent) 77.5 82.9 70.0 studied

Results

From the total of 71 prehistoric Peruvian skulls with complete trepanations, 46 were found to have normal healing, 9 to have partial healing and 16 had no evidence of healing (Table I ) . One skull had both healed and partially healed trepanations (Tables 2a and 3: specimen 1915- 2-310) and another had both unhealed and partially healed trepanations (Tables 2b, 3 and 4: specimen 1915-2-282). Specimen 1915-2-310 had three trepanations: two completely healed and one with both healed and partially healed borders. From this collection, a post-operative survival rate of the initial trepanation can be estimated to be 77.5 per cent (Table 1). Of the 11 skulls selected for radiography, four had normal healing and no evidence of active disease (Table 2a: specimens 191 5-2-259, 191 5-2-268, 19 15-2- 287, 1915-2-310); three had both partial healing and signs of bone infection (Table 2b: specimens 1915-2-282, 1915-2-303, 1915-2-31 1) and four had no bone healing (Table 2c: specimens 19 15- 2-284, 1915-2-305, 1915-2-308, 1915-2-309) and no bone infection, except specimen 1915-2- 309. The results of the evaluation of the trepanation defect for evidence of bone healing, partial healing and no healing by radiography and CT scan (Tables 3 and 4) correlated with those

Table 2 (a). Summary of data for healed skulls: evaluation of cranium by observatiodpalpation.

Resultina Presence of Reference in addition Trepanation Total area aperture&) fracture, or

Specimen location(s) affected (cm) (cm) depression Pathology Other findings to 13

1915-2-259 Frontal, left 5.0 diameter 1915-2-268 Parietal, right 4.6 x 6.4 1915-2-287 1. Frontal Extensive-

(Figure l a ) 2. Left parietal entire area to right parietal 12 x 14

191 5-2-31 0 1. Left parietal 10.3 x 6.5 2. Left parietal (combined) 3. Left frontal

extending to left parietal

3.8 x 3.0

1.0x1.9 Healed fracture No 1.1 x1.7 No No 5.0 diameter Two depressions No 0.8 x 1.9

18-20 15, 18, 19 18

3.3 x 2.7 Depressed fracture No Partial healing 15, 18, 20 2.5 x 2.0 on left parietal along frontal 3.8 x 3.0 plus traces of margin of 3rd

fracture lines trepanation

252 N. Cbege et al.

Table 2 (b). Summary of data for partially healed skulls: evaluation of cranium by observatiodpalpation.

Total area Resulting Presence of Reference Trepanation affected aperture(s) fracture, or in addition

Specimen location(s) (cm) (cm) depression Pathology Other findings to 13

191 5-2-282 Left parietal 13.0 x 10.0 7.0 x 4.4 No Signs of healing Fresh cut along 18, 20 extending to possibly and periostititis inferior and left occipital an injury? on left parietal medial margins

and occipital of original aperture-no healing

1915-2-303 Frontal, right 8.0 x 5.0 3.0 x 6.0 Healed fracture Partial healing 15, 18, 20, (Figure 2a) line and signs of 21

inflammation 1915-2-31 1 1. Frontal, right 9.0 x 7.0 8.2 x 3.7 No Healing and Slight difference 15, 18, 20

2. Right parietal 2.5 x 2.5 2.3 x 1.3 No inflammation in texture to right on 1st and colour of temporal trepanation bone suggests

hyperostosis scalp reflection Trace of porotic area of

Table 2 (c). Summary of data for unhealed skulls: evaluation of cranium by observatiodpalpation.

Total area Resulting Presence of Reference Trepanation affected aperture(s) fracture, or in addition

Specimen location(s) (cm) (cm) depression Pathology Other findings to 13

191 5-2-284 1. Right parietal 4.7 x 6.0 (multiple) 1.7 x 3.7 Right parietal Trace of porotic 15, 18, 20, 2. Left parietal Small (2) 0.3 x 0.5 fracture hyperostosis 22, 23

Healed on parietals depression, and occipital frontal, left

both parietals, hyperostosis especially right on parietals

(Figure 3a) reflection

191 5-2-305 Sagittal suture to 2.3 x 3.0 2.3 x 3.0 Nasal fracture Traces of porotic 18, 20

191 5-2-308 Bregma 3.0 x 1.7 3.0 x 1.7 No No Signs of scalp 18, 20, 24

around trepanation

191 5-2-309 Glabella and right Evidence of

indicates temporal survival after previous injury or trepanation

frontal squama inflammation (multiple) 9.0 x 6.0 18, 20

obtained from gross examination (Tables 2a-c) except for specimen 1915-2-284. In this study, gross examination showed no healing (Table 2c) when both radiography and CT scan showed partial healing (Tables 3 and 4). No bone healing could be demonstrated in specimen 191 5-2-308 visually (Figure 1 a), radiologically (Figure 1 b) or by CT scan (Figure Ic). Partial healing in specimen 1915-2-303 was shown by gross examination (Figure 2a), radiography (Figure 2b) and CT scan (Figure 2c and 2d). Complete

healing of specimen 1915-2-268 could be illu- strated visually (Figure 3a), radiologically (Figure 3b) and by CT scan (Figure 3c). In all specimens, evidence of bone healing was demonstrated better by CT scan than by radiography because the superimposed images of radiography made it difficult to interpret results.

Of the 11 skulls selected for radiography, four showed fracture lines extending from the trepanation opening and strongly suggested an indication for the operation (specimens 191 5-2-

Eoaluation of Skull Trepanation 253

Table 3. Radiographic findings.

Specimen New bone formation Other findings Fracture/pathology

191 5-2-259 1915-2-268 191 5-2-287

1915-2-310 191 5-2-282

(Figure 2b)

191 5-2-303 (Figure 1 b)

1915-2-31 1 1915-2-284 1 91 5-2-305 1915-2-308

(Figure 3b) 191 5-2-309

Yes Yes (definitely) Yes

Yes, in all three defects Yes, partial in superior and anterior

Yes, partial in superior portion only

Yes, partial in small defect Yes, partial None None

None

portions only

Well-defined margins of the defect Well-defined margins of the defect Well-defined margins of the defect

Three well-defined lesions Inferior portion is well-defined, corresponding

No evidence of infected bone

No evidence of new bone in the large defect Well-defined margins of defect Sharp margins of defect Sharp margins of defect

Sham marains of defect

to fresh cut

Healed fracture line None None

Healed fracture lines None

Healed fracture line

None None None None

None

Table 4. CT scan findings.

Specimen New bone formation Other findings Fracture/pat hology

1915-2-268

191 5-2-287

191 5-2-282 (Figure 2c)

191 5-2-303

1915-2-311

191 5-2-284 191 5-2-305 191 5-2-308

(Figure lc)

(Figure 3c) 191 5-2-309

Yes, large area

Yes

Yes, partial on superior border

Yes, partial in superior portion only

Yes, partial in small defect

Yes, partial None None

None

Calvarium thickening in new bone

None

Sharp margins on inferior margin

No evidence of new bone formation in

Evidence of fresh cut on large defect

No evidence of healing in some areas Sharp margins of defect Sharp margins of defect

Sharp margins of defect

suggest no healing

inferior portion

Extensive irregular bone reconstruction

None

Possible periostitis versus partial healing

Radiolucent areas in cortex suggest bone

Radiolucent areas in cortex suggest bone

None None None

Radiolucent area in cortex suggests bone

suggests infection

on both margins

infection; fracture line

infection in large defect

infection

259, 1915-2-310, 1915-2-303 (Figure Za-c), and specimen 1915-2-284). Except for speci- men 1915-2-284, these fracture lines were illustrated by all three methods (gross exam- ination, radiography and CT scan), neither CT nor radiography could demonstrate a fracture line of skull 1915-2-284. However, CT would have shown the fracture line if the two- dimensional slice had been cut perpendicular to the fracture.

Traumatic skull injury, with resulting bone infection, as an indication for trepanation was also suggested in four specimens (1915-2-282, 1915- 2-303, 1915-2-31 1, 1915-2-309). In all four, only gross examination CT scan could demonstrate bone infection clearly, as shown by specimen

1915-2-303 (Figure 2a, c). Grossly, the sharp borders of a fresh cut are seen on an irregular pitted surface of an infected bone (Figure 2a). By CT scan, the radiolucent areas in the cortex adjacent to the sharp margins of a fresh cut suggest bone infection (Figure 2c). Radiography of these skulls did not suggest bone infection. In all four specimens, injury to the skull seems to have lead to periostitis (specimen 1915-2-282) or osteomyelitis (specimen 19 15-2-303, 19 15-2- 311, 1915-2-309). In three other cases gross examination showed evidence of porotic hyper- ostosis (1915-2-31 1 , 1915-2-284, 1915-2-305), but it is questionable whether this was a reason for trepanation. A more obvious indication, trauma, is clearly demonstrated in two of these

254 N. Cbege et al.

Figure 1. (a) Skull 1915-2-308. Photograph of unhealed trepanation. The opening shows porosity of a fresh cut. No sign of trauma. (b) Radiograph of skull showing sharp margins of defect with no evidence of new bone formation. (c) CT scan of unhealed trepanation. Sharp margins of defect can be seen with no bone regeneration.

specimens ( 1 9 15-2-3 1 1 shows injury and bone infection and 191 5-2-284 shows fracture lines). No hyperostosis was seen by CT scan or We have shown that both radiography and CT radiography. scan demonstrate with considerable accuracy the

Discussion

Evaluation of Skull Trepanation 255

presence or absence of new bone formation on scan correlates well with gross examination in all trepanned pre-Columbian skulls. Our data show but one case (specimen 1915-2-284). In this case, that evidence of complete healing, partial or early gross examination revealed traces of porotic healing and no healing by radiography and CT hypero~tos is '~ and three unhealed fracture lines

(continued on next page)

256

(one large and two small) radiating from the right parietal site of trepanation. The latter strongly suggests that the patient was operated on for relief of a depressed fracture.I8 Both radiography and CT scan showed partial healing, implying that the patient had survived for some time following the operation. Although no healing was noted by our gross examination or that of Merbs,'3 our CT and radiography data confirm the finding of Moodie and R0gers ,~51~~ who describe the specimen as showing some evidence of bone healing.

In comparing CT with radiography our data show that the superimposed images of the latter make it more difficult to interpret results. Consequently, radiography is less reliable than CT in differentiating the presence or absence of new bone formation at the margins of a trepanation defect. Furthermore, the data show that unlike CT, radiography could not demon- strate bone infection clearly. In addition, CT was better than radiography in demonstrating skull fractures when the images are cut perpendicular to the fracture lines. Our data show that the two-

N. Cbege et al.

dimensional slices of CT scan created superior images, second only to gross examination.

From the gross examination of the 71 skulls with complete trepanation, the survival rate was estimated to be 77.5 per cent. This finding is consistent with the high surgical success rate noted by others,5f8,15J5J6 but, of course, a mortality rate of 22 per cent would be unacceptable by modern standards. The apparently high post- operative mortality rate may be due to the presence of post-mortem trepanations. It has been suggested that inexperienced young Peruvian surgeons may have practised trepanation on the dead to improve their skill or as part of an autopsy.19,20,23 Macroscopic examination of un- healed trepanation for evidence of temporary survival without new bone formation is difficult and a subject of controversy.26 According to Stewart, evidence of bone reaction to damage (referred to as osteitis) is an indication of a brief post-operative survival. This appears as porosity of the surface of the bone surrounding fresh trepanation cuts. In this study, neither radio- graphy nor CT scan could unquestionably

Figure 2. (a) Skull 1915-2-303. Photograph of partially healed trepanation. The pitted surface around the opening suggests bone infection. Healed fracture lines extending out from the superior border of the opening may suggest reason for the operation. (b) Radiograph showing partial healing in superior portion of defect and well-defined margins of unhealed defect in the inferior portion. Healed fracture line can be seen. No evidence of infection by radiography. (c) CT scan. Partial healing in superior border and no healing in inferior margin. Radiolucent areas in cortex suggest bone infection. (d) CT scan showing fracture line.

Eualuation of Skull Trepanation 257

Figure 3. (a) Skull 1915-2-268. Photograph of healed trepanation. The opening shows smooth, irregular borders, a closed diploe (inner and outer plates fused) and few osteophytes. The opening is surrounded by an irregular surface with multiple depressions. (b) Radiograph showing healing. New bone is more radiolucent and with less mature architecture compared with surrounding old bone. Margins of defect are well defined, smooth and irregular. (c) CT scan of healed lesion. Extensive, irregular, less mature and more radiolucent bone reconstruction is demonstrated. Findings suggest that healing may have been complicated by infection.

258

distinguish post-mortem from ante-mortem tre- panation. O u r radiographic data confirm the finding of Schroder w h o believes it is practically impossible to radiologically differentiate trepana- tions done o n live patients from those done on the dead.6r27

A high mortality could also have resulted not from the operation itself, but from the original injury that lead to trepanation. Both CT scan and gross examination demonstrated several skulls with bone infection a n d early signs of healing. Data suggested traumatic injury followed by bone infection was one reason for trepanation.

To conclude, of the three techniques used in this study, macroscopic examination remains the gold standard method to evaluate pre-historic trepanned skulls. CT is by far superior to radiography and correlates better with gross examination.

N. Cbege et al.

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