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raniectomy: Surgical Indications and Technique

artin Holland, MD, and Peter Nakaji, MD

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ntractable intracranial hypertension in trauma patients is asso-iated with high rates of morbidity and mortality. Decompressiveraniectomy offers a treatment option for this otherwise direituation. This article illustrates the techniques for both unilateralemicraniectomy and bifrontal craniectomy. The skin incisions,egree of bone removal, and options for dealing with the boneap are discussed.opyright 2004, Elsevier Inc. All rights reserved.

n the United States trauma is the leading cause of death inindividuals between the ages of 1 and 44 years. Most of these

eaths are attributable to traumatic brain injury (TBI). Amonghe many problems that follow TBI, intracranial hypertension ismajor cause of complications and death. Consequently, neu-

osurgeons devote considerable effort to controlling intracra-ial pressure (ICP) in patients with TBI. Decompressive crani-ctomy has been advocated as one strategy for managing ICP.his article discusses the principles, indications, surgical anat-my, and technique associated with decompressive craniec-omy.

Principles

here are two phases of brain injury. The primary phase occurst the moment of impact. The secondary phase occurs in theinutes, hours, or days after the initial injury. The concept of

econdary injury is supported by both animal and clinical stud-es that indicate that injured tissue is highly vulnerable to in-ults readily tolerated by uninjured tissue. Secondary injury ishe single most important treatable cause of neurological deficitnd death after TBI.

Intracranial hypertension is a major cause of secondary brainnjury and often follows trauma or stroke. Because ICP variesith changes in the volume of the intracranial contents, the

raditional approach for treating intracranial hypertension haseen to reduce the volume of one or more of the compartments,hich include brain parenchyma, cerebrospinal fluid (CSF),

nd blood volume, either surgically or nonsurgically.An alternate approach is to increase cranial volume by re-oving the skull and opening the dura. The underlying brain

an then swell under the relatively distensible skin. The use of

From the UCSF Department of Neurological Surgery, University ofalifornia, San Francisco, Clinical Director Brain and Spinal Injury Center,an Francisco, CA, USA and Division of Neurological Surgery, Barroweurological Institute, St. Joseph’s Hospital and Medical Center, Phoe-ix, AZ.Address reprint requests to Peter Nakaji, MD, Neuroscience Publica-

ions, Barrow Neurological Institute, 350 W. Thomas Road, Phoenix, AZ5013.Copyright 2004, Elsevier Inc. All rights reserved.1092-440X/04/0701-0003$30.00/0

hdoi:10.1053/j.otns.2004.04.006

Operative0

ecompressive craniectomy to control ICP has been advocatedor a number of disease processes, including stroke, tumors,nd trauma. The rationale for decompressive craniectomy is torevent secondary injury caused by intracranial hypertension.

Indications

here are no widely accepted indications for craniectomy. Mosttudies are retrospective. In the few available prospectivetudies, the procedure has been performed in patients withedically refractory intracranial hypertension. Coplin and co-orkers, however, suggested that early “prophylactic” decom-ressive craniectomy may be of some benefit. ICP is easier toontrol after a craniectomy, and the therapeutic intensity of ICPanagement is decreased in patients who have had craniecto-ies.1 However, data correlating craniectomy and improved

utcome are suggestive at best.1-6

Early decompressive craniectomy can be considered for pa-ients undergoing emergent evacuation of a hematoma. It iseasonable to entertain craniectomy as a treatment option. Theecision to leave the bone flap off can be made intraoperativelyased on the patient’s mechanism of injury; age; degree ofnderlying cerebral swelling, atrophy, or both; and the sur-eon’s estimation of the likelihood that the patient will developevere intracranial hypertension.

Patients with significant cerebral atrophy (eg, chronic alco-olics) are less likely to develop intracranial hypertension thanatients with full brains, primarily because they are able toolerate mass lesions better. Patients with subdural hematomasaused by severe acceleration and deceleration forces oftenave significant underlying brain injury and are more likely toevelop brain swelling and subsequent intracranial hyperten-ion. Such patients may benefit from a craniectomy. If theurgeon decides that a patient is likely to develop intracranialypertension, he or she may opt to leave the bone flap off withhe idea of performing a cranioplasty in the future.

Although craniectomies decrease ICP, complications are alsossociated with the procedure. If the bone flap is too small, therain may mushroom through the opening and catch on thedge of the craniectomy. The brain can be damaged by directressure, possibly causing congestion of compressed corticaleins. Another common postoperative problem is the develop-ent of interhemispheric or contralateral subdural hygromas

r both. Hygromas are likely caused by deranged patterns ofSF flow in the presence of low ICP.

Surgical Technique

raniectomies can be divided into two categories: hemicrani-ctomies and bilateral craniectomies. Hemicraniectomies in-olve the removal of bone along one hemicranium whereasilateral craniectomies involve the removal of bone from both

emispheres. The surgical technique for both is described.

Techniques in Neurosurgery, Vol 7, No 1 (March), 2004: pp 10-15

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emicraniectomy

he ideal hemicraniectomy involves the removal of bone alonghe entire supratentorial hemicranium. It is essential to under-tand the relationship between external and internal anatomi-al features such as the floor of the frontal and temporal fossand the lateral tentorial attachments. The root of the zygoma,hich identifies the floor of the temporal fossa, is the most

mportant landmark for performing this procedure.Other important landmarks include the inion, asterion, mid-

ine, keyhole, and glabella. The asterion, which marks the con-uence of the lamboid, occipitomastoid, and temporoparietalutures, indicates the area of transition between the transversend sigmoid sinuses. The superior extent of the transverse sinusypically is found 1-cm rostral to the asterion. The great sinusonfluence usually underlies the inion. Thus, a line extendingrom the root of the zygoma toward the inion and across thesterion demarcates the inferior extent of the temporal andccipital lobes.The keyhole, another important landmark, identifies the pte-

ion and indicates the location of the frontal, temporal, andrbital cavities. The floor of the frontal fossa is usually 1-cmuperior to the keyhole. The temporal tip underlies a point-cm posterior and inferior to the keyhole. The lateral orbitalall is about 1-cm anterior and inferior to the keyhole. Theidline delineates the course of the superior sagittal sinus.lthough the goal of the hemicraniectomy is to remove as muchone as possible, the surgeon must avoid injuring the superioragittal and transverse sinuses.

Equally important as an understanding of the limits of bonyemoval is an understanding of the skin incisions and position-ng that allow the surgeon to expose the entire hemicranium sohat the craniectomy can be performed without difficulty.

We prefer to place the patient in a Mayfield headholder (Cod-an, Inc. Raynham, MA) even though this maneuver requires

xtra time. Two other options are to place the patient in a

ig 1. The incision for unilateral hemicraniectomy is similaro the usual trauma flap but covers a larger area to allow

cccess to the entire hemicranium for bone removal.

RANIECTOMY

orseshoe headholder or donut. We prefer the Mayfield head-older because it enables easier access to the entire hemicra-ium. The draping and skin incisions are thereby easier toerform. Furthermore, the head is held firmly in position foretraction of the skin flap and for the subsequent craniectomy.

e also prefer to use a Leyla bar (Aesculap®, San Francisco,A) to support the skin retractors. The Mayfield headholder,owever, is inappropriate for patients with severe diffuse com-inuted skull fractures.The Mayfield pins are placed low and out of the way of the

ncision. The two-prong side supports the suboccipital area,nd the single-pronged end is placed on the contralateral fore-ead. By placing the pins in these locations, the entire hemicra-ium is accessible for shaving, sterile preparation, draping, andhe surgical procedure.

Once the patient’s head is placed in the Mayfield headholder,he ideal position is for the sagittal plane of the head to beorizontal to the floor. This position is not always possible tottain because the patient’s cervical spine is not always clearedefore surgery. Some patients also have stiff cervical spines.nder such circumstances, the patient’s head is turned as far as

s reasonable. The remainder of the turn can be achieved byilting the table. Tilting requires that the patient be securelyaped to the table.

To perform a full hemicraniectomy requires exposure of thentire hemicranium. Two incisions permit this goal to bechieved. The first option is a curvilinear incision that begins athe widow’s peak and continues posteriorly along the midlineo the inion (Fig 1). It then turns sharply to the ear parallel to aine extending from the inion to the root of the zygoma. Thencision should skirt the superior and anterior portions of thear as closely as possible and extend 1 cm below the root of theygoma.

This incision achieves several goals. First, the entire hemi-

ig 2. The T-shaped incision has the advantage that it canasily be expanded. Although less familiar to most neurosur-eons, this incision provides easy access to the entire hemi-ranium and leaves flaps with a more robust blood supply.

ranium is exposed at the midline. Second, the bone is exposed

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long the line of the transverse sinus. The amount of temporalossa exposed is also increased. Hugging the ear avoids theuperficial temporal artery, thus providing maximal blood flowo the most distal corner of the skin flap. This blood supply isost compromised at or near the inion.Once the skin incision is made, usually with a No. 10 blade,

he periosteum can be incised with an electrocautery knife. The

ig 3. (A) The extent of bone removal for the unilateral hemi-raniectomy is illustrated. Unintentional underremoval ofone is a common pitfall. (B). Computed tomography (CT)can of a typical case. Bone is left posteriorly for the head toest on. In this case, more bone could have been removednteriorly.

utaneous flap can then be manually reflected anteriorly with t

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he aid of a surgical sponge. At this point there are two optionsor reflecting the temporalis muscle. The first option allows thekin to be reflected anteriorly as a separate layer of muscle. Thisaneuver allows the temporalis muscle to be reflected with

elative ease.The second option involves reflecting the muscular and cu-

aneous flaps together; the skin flap is not separated from theemporalis muscle. The advantage of this option is that theuscle remains attached to the overlying scalp, keeping theuscle in position in the absence of an underlying attachment

o the bone. We prefer this option because it preserves theuscle and improves cosmesis when the bone flap is returned.he major advantage of the curvilinear incision is that it isuick and easy. Its major disadvantage is the potential risk ofap ischemia and dehiscence of the wound, particularly at itsosterior margin.The alternative skin incision for a hemicraniectomy is similar

o that described for a hemispherectomy. A midline incisionxtends from the inion to the widow’s peak. Then, a “T” inci-ion is created by extending another limb from about the coro-al suture down to a point 1 cm inferior to the root of theygoma (Fig 2). With this incision, the blood supply to bothkin flaps is much more robust than with the curvilinear inci-ion. However, it requires slightly more time to execute and is aittle tricky. As with the curvilinear incision, the temporalis

uscle can be incised along with the skin or it can be handleds a separate layer.

We recommend preserving the superficial temporal artery byrst starting the T incision behind the coronal suture. The

ncision continues inferiorly and ends as close to the anteriorortion of the ear as possible. With this technique, we have seeno dehiscence of the posterior portion of the incision.Once the skin incision has been made and the entire hemi-

ranium has been exposed, fishhooks are used to retract the

ig 4. The bone flap can be inserted into an abdominalocket. The pocket must be large enough to provide a

ensionless closure.

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kin flap inferiorly. In the case of the curvilinear incision, thekin flap is retracted anteriorly. In the case of the T incision, thekin is retracted both anteriorly and posteriorly. A single burole is made just superior to the root of the zygoma, whichelineates the floor of the temporal fossa. Some piecemeal re-oval of bone inferiorly may be required to reach the floor. The

sterion should be exposed by reflecting the soft tissue cau-ally. This maneuver allows visualization of the inferior extentf the temporal and occipital lobes.

ig 5. (A) A typical bicoronal incision is sufficient to createifrontal craniectomy is shown. Special care must be takenegion. CT scans on bone windows (C) and brain windowsindows. (Continued on next page)

Once the bur hole is made, the footplate is inserted. The bone u

RANIECTOMY

ap is turned by extending the beginning of the craniectomylong the line toward the inion. To avoid injuring the transverseinus, it is best to stay at least 1-cm rostral to the asterion. As theone flap is extended posteriorly, the lambdoid suture isrossed. At this point, the drill bit is turned parallel to and 1-cmedial to the lambdoid suture until the surgeon reaches a pointcm from the midline. The drill is then turned parallel to the

agittal sinus, again crossing the lambdoid suture. Drilling con-inues toward the supraorbital bar. The craniotomy is contin-

frontal craniectomy. (B) The extent of bony removal for themove the bone along the supraorbital rim and subtemporalhow the craniectomy. (E) CT scan shows the subtemporal

a bito re(D) s

ed anteriorly by hugging the floor of the frontal fossa as closely

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s possible, staying as close to the orbital rim as the anatomyllows.

Next, the drill is turned posterolaterally toward the keyholend aimed as close to the pterion as possible. At this point, therill is removed and re-inserted into the bur hole at the root ofhe zygoma. The second drill line is created by hugging the floorf the temporal fossa and extending it as far anteriorly as pos-ible toward the temporal tip. The bone flap is removed byevering it using the pterion as fulcrum. Usually the pterionracks on removal and the dura can be dissected using Rhotonissectors. The full extent of bone removal is illustrated inig 3.Once the bone flap is removed, Leksell rongeurs are used to

emove excess bone at the temporal floor and temporal tip,ateral floor, and pterion. Care is taken to ensure that the bonedges are smooth so the brain does not catch on an edge as itwells laterally. The dural opening extends in a C-shaped fash-on from the temporal tip to the frontal pole. To maximize thepening, the dural incision should run within 1 cm of the bonydge. Thus, the dural flap is based on the pterion and can beeflected anteriorly to expose the hemisphere.

Dural release incisions can be performed on the dural edgextending to the bone edge. This maneuver minimizes cerebralemisphere catching on the dura as it swells laterally. If needed,eripheral dural tack-up stitches can be placed to control epi-ural hemorrhage.At this point, underlying hematomas can be evacuated. In the

ase of subdural hematomas, the bridging veins can be accessedo ensure that they are no longer bleeding. Once hemostasis isnsured, the dura can be laid back on the brain. A large piece ofelfilm® (Upjohn, Kalamazoo, MI) is placed along the entireemicranial defect to make subsequent dissection for a cranio-lasty easier to perform. The skin is closed over the Gelfilmsing 2-0 Vicryl (Ethicon, Johnson & Johnson Professionals,nc., Somerville, NJ) stitches for the galea. Typically, staples aresed to close the skin.There are three options for dealing with the craniectomy

Fig 5. (Cont’d)

one flap. One is to discard it. The second is to create a separate l

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bdominal subcutaneous incision to place the bone flap, whichs then accessed at the time of the cranioplasty (Fig 4). The thirds to preserve the bone flap in a tissue bank. We prefer the lastption. Discarding the flap requires that the cranioplasty beerformed with intraoperative reconstruction, usually titaniumesh, methylmethacrylate cement, or with a prefashioned

omputer-generated bone flap. Cosmetically, these options areuboptimal and more expensive than using the patient’s ownone. Placing the bone flap in the abdominal subcutaneousavity is an acceptable alternative. However, the body usuallyemolds the bone edges to some degree, leaving it knobby andlightly enlarged. This remolding adversely affects the ability tobtain a tight bone edge at the time of cranioplasty. Keeping theone frozen in a bone bank is associated with excellent cos-etic outcomes. There is no risk of bone remodeling and re-

lacement is easy. An alternative technique involving ethylenexide sterilization and preservation at room temperature haslso been described.7

ilateral Craniectomies

n alternative method of cranial decompression is to removehe skull bone bilaterally. Two options also exist for thisethod. The first involves performing two hemicraniectomies

s described above. A strip of bone about 2 to 3 cm wide is leftlong the midline covering the superior sagittal sinus. Eitherncision described above can be used. However, a second hemi-raniectomy usually precludes use of the Mayfield headholder.he technique is otherwise identical.Alternatively, a bifrontal craniectomy has been described by

enes and Collins,8 Polin and co-workers,9 and Fisher andjemann,10 among others. Posterior to the coronal suture, a

oronal incision is extended from 1 cm below the root of theygoma bilaterally to the vertex. The musculocutaneous flap isetracted anteriorly and inferiorly to expose the frontal andemporal areas down to the floor of the temporal fossa bilater-lly.

Bur holes are made at the root of the zygoma bilaterally. Therst cranial drill line extends from zygoma to zygoma crossinghe superior sagittal sinus. We do not place bur holes on eitheride of the superior sagittal sinus to perform subsequent duralissection, although this technique has its proponents.Two other bur holes can be placed at the keyhole bilaterally.second dural line extends from keyhole to keyhole across theidline about 1 cm parallel and superior to the orbital rim. This

ine crosses the floor of the frontal fossa. Crossing midline isometimes difficult because the inner table of the bone divesnward. If this situation is encountered, the cranial drill line isreated bilaterally toward the midline. The gap can be jumpedsing osteotomes.The final two drill lines are made from the zygomatic bur

ole anteriorly by hugging the floor of the temporal fossa to-ard the temporal tip and extending superiorly and anteriorly

oward the keyhole. The bifrontal craniectomy can then beemoved as one piece (Fig 5). The subtemporal craniectomyan be enlarged in piecemeal fashion with a Leksell rongeur.

Alternatively, the bifrontal craniectomy can be removed inwo pieces by leaving a strip of bone attached to the superioragittal sinus at the midline and performing two craniectomiesFig 6). This technique is most useful for patients whose pri-ary problem is bilateral frontal contusions. The dura is re-

eased by making a C-shaped dural incision that extends from

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he temporal tip along the floor of the temporal fossa andontinues posteriorly and superiorly parallel to the posteriordge of the craniectomy site toward the superior sagittal sinus.he dural incision extends from the frontal pole laterally, hug-ing the floor of the frontal fossa toward the pterion. As de-cribed for the hemicraniectomy, the bone of the temporal androntal fossae and pterion should be shaved with Leksell ron-eurs. The bony rims are smoothed so that egress of the swollenrain will not be impeded. This maneuver also permits theural incision along the floor of the frontal fossa to connectith the dural incision at the temporal tip. Thus, a large duralap is created based on the superior sagittal sinus bilaterally.Gelfilm is placed over the entire craniectomy defect. The skin

s closed with 2-0 Vicryl sutures and stapled. The bone flap cane handled as described in the section on hemicraniectomy.The timing of bone flap replacement or cranioplasty is left to

he discretion of the surgeon based on the patient’s clinicaltatus. We typically offer placement 6 months after the cranio-

ig 6. The alternate technique of bifrontal craniectomy islmost identical to the unilateral technique except that theone is taken in two flaps, sparing the midline. To avoidotential harm to the swollen brain, the strip left in the middleust not be too wide.

RANIECTOMY

lasty to allow the underlying brain to have recovered maxi-ally and to minimize the risk of infection.Neurological recovery after cranioplasty has been docu-ented11,12 (about 50% of cases in our experience). Recovery

sually involves improved motor strength or language functionithin the first several weeks of the cranioplasty.

Conclusions

ecompressive cranioplasty is an effective technique for de-reasing ICP and for decreasing the intensity of therapy neededo control intracranial hypertension. Clear-cut indications forerforming such a procedure have not yet been delineated. Arospective, randomized study is needed. Nevertheless, anec-otal experience and the outcomes of preliminary studies ofraniectomies suggest that this option may be viable for pa-ients at risk for developing high ICP after stroke or trauma.

References1. Coplin WM, Cullen NK, Policherla PN, et al: Safety and feasibility of

craniectomy with duraplasty as the initial surgical intervention forsevere traumatic brain injury. J Trauma 50:1050-1059, 2001

2. Albanese J, Leone M, Alliez JR, et al: Decompressive craniectomy forsevere traumatic brain injury: Evaluation of the effects at one year.Crit Care Med 31:2535-2538, 2003

3. Figaji AA, Fieggen AG, Peter JC: Early decompressive craniotomy inchildren with severe traumatic brain injury. Childs Nerv Syst 19:666-673, 2003

4. Soukiasian HJ, Hui T, Avital I, et al: Decompressive craniectomy intrauma patients with severe brain injury. Am Surg 68:1066-1071,2002

5. Kontopoulos V, Foroglou N, Patsalas J, et al: Decompressive crani-ectomy for the management of patients with refractory hypertension:Should it be reconsidered? Acta Neurochir (Wien) 144:791-796, 2002

6. Guerra WK, Gaab MR, Dietz H, et al: Surgical decompression fortraumatic brain swelling: Indications and results. J Neurosurg 90:187-196, 1999

7. Missori P, Polli FM, Rastelli E, et al: Ethylene oxide sterilization ofautologous bone flaps following decompressive craniectomy. ActaNeurochir (Wien) 145:899-902, 2003

8. Venes JL, Collins WF: Bifrontal decompressive craniectomy in themanagement of head trauma. J Neurosurg 42:429-433, 1975

9. Polin RS, Shaffrey ME, Bogaev CA, et al: Decompressive bifrontalcraniectomy in the treatment of severe refractory posttraumaticcerebral edema. Neurosurgery 41:84-92, 1997

0. Fisher CM, Ojemann RG: Bilateral decompressive craniectomy forworsening coma in acute subarachnoid hemorrhage. Observationsin support of the procedure. Surg Neurol 41:65-74, 1994

1. Gottlob I, Simonsz-Toth B, Heilbronner R: Midbrain syndrome witheye movement disorder: Dramatic improvement after cranioplasty.Strabismus 10:271-277, 2002

2. Segal DH, Oppenheim JS, Murovic JA: Neurological recovery aftercranioplasty. Neurosurgery 34:729-731, 1994

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