ORIGINAL ARTICLE

Treatment of chronic subdural haematomas – A retrospectivecomparison of minicraniectomy versus burrhole drainage

MARK WHITE1, CALAN S. MATHIESON1, EMER CAMPBELL1, KEN W. LINDSAY1 &

LILLIAN MURRAY2

1Institute of Neurological Sciences, Southern General Hospital, Glasgow, United Kingdom and 2Department of Statistics,

Glasgow University, Glasgow, United Kingdom

AbstractPrimary chronic subdural haematomas remains one of the commonest conditions managed by neurosurgeons. Despite thisthere is a relative lack of evidence regarding best management and certain treatments such as minicraniectomy, have rarelybeen assessed in the literature. A retrospective case note review comparing minicraniectomy and burrhole drainage ofprimary chronic subdural haematoma was therefore performed. We sought to determine the proportion of patients requiringrepeat drainage or dandy cannula aspiration following initial surgery and to assess outcome at outpatient follow-up. Themean age of patients undergoing minicraniectomy was 73, compared to 63 in the burrhole group (p5 0.001). 130 patientsunderwent burrhole drainage, 23 of whom (18%) developed a symptomatic recurrence. 21 (16%) of these patients requiredrepeat drainage. Of the 116 patients who underwent a craniectomy 23 (20%) patients suffered a symptomatic recurrence. 15(13%) patients required the minicraniectomy to be reopened for further washout (p¼ 0.48). (8%) patients who underwentburrhole drainage died compared to 20 (17%) patients following craniectomy (95%CI 2 to 18%; p¼ 0.03). However,controlling for age using logistic logression, showed no significant difference between the two treatment groups in recurrence(p¼ 0.28) or death (p¼ 0.06). Craniectomy may be considered as a treatment option particularly in the elderly populationand in patients with multiple loculated collections.

Key words: Chronic subdural haematoma, burrhole drainage, minicraniectomy, recollection.

Introduction

Primary chronic subdural haematomas remains one

of the commonest conditions managed by neurosur-

geons. A variety of different surgical treatments exist,

including twist drill craniostomy, single or multiple

burrhole drainage (with or without a subdural drain),

minicraniectomy and craniotomy. Santarius et al.1

recently published class 1 evidence for the use of

subdural drains in treating this condition. Weigel

et al.2 published a meta-analysis in 2003, concluding

that burrhole drainage was more effective in draining

a chronic subdural haematoma than twist drill

craniostomy, and was associated with fewer compli-

cations than craniotomy. In an abstract, Goyal et al.3

presented a small non randomised prospective trial of

craniectomy and burrhole drainage, concluding that

craniectomy and burrhole drainage were effective at

treating chronic subdural haematoma. The aim of

this study was to complete a retrospective compar-

ison of minicraniectomy and burrhole drainage. We

sought to determine the proportion of patients

requiring repeat drainage or Dandy cannula aspira-

tion following initial surgery and to determine

outcome in each group.

Methods

We reviewed retrospectively all adult patients with a

primary chronic subdural haematoma treated in our

Institute between the 1st of January 2003 and the 31st

December 2005. Patients were excluded if the

collection was secondary to an overdraining ventri-

culoperitoneal shunt. All patients undergoing either

burrhole drainage or minicraniectomy were included

in the study. The choice of surgical technique was

made by the responsible consultant (any of the 8

consultants in the Institute). The decision to treat

with minicraniectomy was largely made in the older

patients with multiple loculations on CT scan.

We recorded basic patient demographics, pre-

operative neurological condition, a pre-operative

history of coagulopathy or use of anticoagulants or

antiplatelet drugs, history of alcohol abuse, in

addition to the appearance and size of the haemato-

ma on CT scan. The primary endpoint was a

Correspondence: Calan S. Mathieson, Southern General Hospital, Neurosurgery, Glasgow, United Kingdom. Tel: 0141 201 1100.

E-mail: calan@doctors.org.uk

Received for publication 11 August 2009. Accepted 2 February 2010.

British Journal of Neurosurgery, June 2010; 24(3): 257–260

ISSN 0268-8697 print/ISSN 1360-046X online ª The Neurosurgical Foundation

DOI: 10.3109/02688691003675218

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symptomatic recurrence that required intervention,

either percutaneous aspiration or re-operation. Sec-

ondary endpoints included the Glasgow Outcome

Score at three month follow-up, any documented

improvement in preoperative conscious level or focal

neurological deficit and mortality at three months. Of

246 patients, 130 underwent burrhole drainage and

116 patients were treated by minicraniectomy.

Mean values were compared using 2-sample

t-tests/confidence intervals, and confidence intervals

for proportions were calculated using a normal

approximation. For comparison of proportions p-

values were calculated using Fisher’s exact test. A

logistic regression was used to model the effect of

treatment on outcome controlling for the effect of

other variables. Confidence intervals quoted are for

differences between groups. All tests were 2-sided

and calculated using Minitab version 15.

The surgical technique for minicraniectomy in-

volved making a small bone flap of diameter 3–5 cm,

usually by drilling 2 to 3 burrholes and connecting

them using the craniotome.. The bone flap was not

replaced at the end of the procedure. The dura was

incised, the edges diathermied and the subdural

space washed out (Fig. 1). The craniectomy enabled

breakdown of any visible loculations within the clot

cavity and if necessary, permitted diathermy and

division of bridging veins. Following removal of the

haematoma, the subdural space was filled with saline,

and attempts were made to minimise the capture of

air in this space during closure. Subdural drains were

not routinely inserted for either minicraniectomy or

burrhole drainage.

Results

Over the 3-year period, 268 patients were treated

surgically for primary chronic subdural haematoma,

22 patients underwent a craniotomy and were

excluded, 130 patients underwent burrhole drainage

(3 with subdural drain) and 116 patients were treated

by craniectomy 1 with subdural drain (Figure 3).

The majority of patients were male both in the

burrhole group (72%), and in the craniectomy group

(66%). The mean age of patients undergoing mini-

craniectomy was 73 years, compared to 63 years in the

burrhole group (95%CI 6 to 13 years); p50.001). In

the burrhole group, 37 (28%) patients had received

anticoagulants or antiplatelet therapy (aspirin, clopido-

grel and persantin), compared to 45 (39%) in the

minicraniectomy group (95% CI71 to 22%; p¼ 0.10);

37/130 (28%) of the burrhole group and 21/116 (18%)

of the minicraniectomy group had a history of alcohol

abuse (95% CI 0 to 21%; p¼ 0.07). The average depth

of the haematoma as demonstrated on CT scan, was

comparable (22 mm burrhole vs 23mm minicraniect-

omy) between the two groups (95%CI 74 to 5 mm;

p¼ 0.82), but the mean midline shift was greater in the

craniectomy group (5.4 vs 6.9 mm; 95%CI 0.3 to

2.8 mm; p¼ 0.02). Of 129 of 130 burrhole procedures,

registrars performd 129 and a consultant performed

one; of the 116 craniectomies, registrars performed

112 and consultants performed 4.

Recurrence rate

Of the 130 patients who underwent burrhole

drainage, 23 patients (18%) developed a sympto-

matic recurrence, 21 (16%) requiring repeat drainage

and 2 Dandy cannula aspiration. In 14 patients the

burrholes were converted to a minicraniectomy or

craniotomy (12/2 respectively) to aid further treat-

ment. Of the 116 patients who underwent a mini-

craniectomy 23 (20%) patients suffered a

symptomatic recurrence. In 15 (13%) the minicra-

niectomy was reopened for further washout (95%CI

712 to 5%; p¼ 0.48); the other 8 patients were

treated by Dandy cannula aspiration on the ward.

In patients over 65 years old, 15 of 66 (23%)

patients treated by burrhole drainage developed a

symptomatic recurrence compared to 10 of 93

(10.8%) patients who developed a recurrence in the

minicraniectomy group (p¼ 0.048). In patients with

multiloculated collections seen on CT scan, 2 of 22

patients treated with burrholes required further

surgery compared to 2 of 36 patients initially treated

with minicraniectomy.

Outcome

At the 3-month follow-up period, 10 (8%) patients

who underwent burrhole drainage had died com-

pared to 20 (17%) patients following minicraniect-

omy (95%CI 2 to 18%; p¼ 0.03) (Table I). Of the 30

deaths in the whole cohort, 10 were related to

cardiovascular or respiratory complications, and 2 to

operative site infections; in 18 cases, the cause of

death was either unknown or not recorded. Acute

subdural haematomas did not complicate either

drainage procedure in this study. In the immediate

postoperative period, 56/130 (43%) of the burrhole

patients and 50/116 (43%) of the minicraniectomyFIG. 1. Intraoperative photograph of craniectomy for drainage of a

chronic subdural haematoma.

258 M. White et al.

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group showed improvement in their Glasgow coma

score. In those patients who had a preoperative focal

neurological deficit, 47/73 (64%) improved post-

operatively in the burrhole group compared to 53/80

(66%) in the minicraniectomy group. In those

patients undergoing burrhole drainage who reported

headache preoperatively, 48/55 (87%) noted im-

provement postoperatively compared to 33/38 (87%)

in the minicraniectomy group.

Two patients who were treated with burrholes

developed a subdural empyema compared to three in

the minicraniectomy group. There were no wound

complications within either group. Postoperatively,

12 patients (9%) suffered seizures following burr-

holes compared to 10 patients (9%) in the mini-

craniectomy group. The Glasgow Outcome Score

was recorded for each patient returning for final

clinic.review (median follow-up time 118 days,

interquartile range 100–187 days) A good outcome

was recorded as an outcome score of 4 or 5. At clinic,

64/77(83%) of those who had a burrhole drainage

achieved a good outcome as did 66/90 (73%) of those

who underwent a minicraniectomy (95%CI 73 to

22%; p¼ 0.14). Following burrhole drainage, 66/68

(97%) of those seen at clinic reported their initial

symptoms had improved as did 68/70 (97%) patients

who underwent minicraniectomy. Unfortunately, a

significant proportion of patients were lost to follow-

up (53 burrhole, 26 minicraniectomy).

Predictors of poor outcome

Using logistic regression, to model the effect of

treatment on outcome while controlling for age, there

was no significant treatment effect on further operative

intervention (p¼ 0.28) or on risk of death (p¼ 0.06).

Further exploratory analysis was carried out to

identify predictors of poor outcome. Nine of the 30

patients who died had undergone a repeat surgical

procedure (p¼ 0.02). Antiplatelet therapy (p¼ 0.42),

obliteration of the basal cisterns (p¼ 0.50) or the

presence of loculations in the subdural collection

(p¼ 0.80) were not predictive of death. Using a

logistic regression model to control for age and

treatment effect, repeat surgical procedure (p¼ 0.01)

was still predictive of death.

Discussion

Previous studies have commonly reported sympto-

matic recurrence rate of 10–20%.4–6 In our series the

overall recurrence rate was 18.6%. Various factors

have been identified that increase the likelihood of

recurrence. Amirjamshidi et al.7 concluded that

lower preoperative GCS,, presence of intracranial

air 7 days after surgery and a high density haematoma

were significantly associated with recurrence of the

haematoma. Taussky et al.8 reported that patients

treated with a single burrhole had a significantly

higher chance of recurrence compared to those

treated with two. Abouzari et al.9 showed that

assuming an upright position soon after burrhole

drainage led to a significant increase in recurrence

and Santarius et al.1 recently showed that not using a

subdural drain increases recurrence rates signifi-

cantly in a randomised controlled trial.

Treatment with minicraniectomy has not been

widely evaluated; in a recent review of practice in UK

and Republic of Ireland Neurosurgical centres,10 few

report the use of this technique. Lee et al.10

concluded from his review of 172 chronic subdural

patients treated by either burrhole drainage, cra-

niectomy or craniotomy that the recurrence rates

were similar in all 3 groups. The technique of

minicraniectomy has a number of possible advan-

tages. Bridging veins can be cauterised and divided

under direct vision, subdural loculations can be more

easily broken down to aid complete washout of the

subdural space. Minicraniectomy should, therefore,

be considered when imaging suggests multiloculated

collections. Although our study did not show any

difference in recurrence rates of multiloculated

collections between the two groups, this may reflect

the small number of recurrences seen in patients with

loculated collections.

Postoperatively, the pressure of the subdural space

can be assessed from the bedside following a

minicraniectomy and in certain situations recurrent

subdural collections can be aspirated percutaneously.

This could theoretically reduce the need for re-

operation and general anaesthetic in a vulnerable

group of patients.

Using subgroup analysis, elderly patients (over 65

years) treated by minicraniectomy seemed to have a

lower risk of symptomatic recurrence. Tyson et al.11

theorised that craniectomy could reduce the subdural

space by minimising the mismatch between an

atrophic brain and the cranial cavity — a situation

more commonly found in the elderly.

Disadvantages of treatment with minicraniectomy

include a poorer cosmetic result with a sunken defect

often seen several months following surgery (Fig. 2).

FIG. 2. Common postoperative appearance of minicraniectomy

site.

Treatment of chronic subdural haematomas 259

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The DVLA consider burrholes and minicraniectomy

differently for assessing fitness to drive. Minicra-

niectomy is grouped with craniotomy for treatment

of this condition. Following a minicraniectomy for

chronic subdural haematoma, driving is permitted 6

months after treatment. In comparison, a patient is

deemed fit to drive immediately following burrhole

evacuation, provided that there is no focal neurolo-

gical deficit.

This is not a randomised trial nor a case-matched

series. In our study patients undergoing a minicra-

niectomy were older and as age is recognised as a

predictor of poor outcome, it is not surprising that

more patients died in this group.

In conclusion, this study shows that there is no

significant difference in the recurrence rates between

minicraniectomy and burrhole drainage in the treat-

ment of chronic subdural haematomas and suggests

that minicraniectomy is an effective treatment.

Minicraniectomy should be considered as a treat-

ment option, particularly in the elderly population

and possibly also in patients with multiple loculations

within their collections. We agree with the many

previously published papers, that further randomised

controlled trial would help rationalise treatment.

Declaration of interest: The authors report no

conflicts of interest. The authors alone are respon-

sible for the content and writing of the paper.

References

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management of primary chronic subdural haematomas: a

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2 Weigel R, Schmiedek P, Krauss JK. Outcome of contemporary

surgery for chronic subdural haematoma: evidence based

review. J Neurol Neurosurg Psychiat 2003;74(7):937–43.

3 Goyal K, Fitzpatrick MO, Barlow P. Treatment of large

subacute and chronic haematomas in elderly patients. Br J

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4 Mellergrad P, Wisten O. Operations and re-operations for

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5 Wakai S, Hashimoto K, Watanabe N, Inoh S, Ochiai C, Nagai

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TABLE I. Recurrence rates and outcome measures for burrhole drainage and minicraniectomy

Burrhole drainage Minicraniectomy p value (Fisher’s exact test)

Symptomatic recurrence requiring re-drainage 21/129* (16%) 15/116 (13%) 0.48

Symptomatic recurrence treated

with Dandy cannula aspiration

2/130 (2%) 8/116 (7%) 0.05

Mortality 10/130 (8%) 20/116 (17%) 0.03

Improved GCS post-op. 56/130 (43%) 50/116 (43%) 1.0

Focal deficit improved post-op. 47/73 (64%) 53/80 (66%) 0.87

Headache better post-op. 48/55 (87%) 33/38 (87%) 1.0

GOS 4-5 at follow-up 64/77 (83%) 66/90 (73%) 0.14

Symptomatically improved at follow-up 66/68 (97%) 68/70 (97%) 1.0

*Operation notes missing for 1 case.

FIG. 3. Flow chart showing treated patients and recurrence rates.

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