specific craniotomies

Specific Craniot om ies
1445
94 Specific Craniot om ies
94.1 Post erior fossa (suboccipit al) craniect om y
94.1.1 Indicat ions
To gain access to th e cerebellum , cerebellopon tin e an gle (CPA), to on e vertebral artery, posterior
brain stem , fourth ven tricle, pin eal region , or, usin g extrem e lateral posterior fossa approach to th e
an tero-lateral brain stem . See param edian (p. 1447) an d m idlin e (p. 1450) suboccipital cran iectom ies
for details.
94.1.2 Posit ion
Opt ions
Position opt ion s in clude:
1. sitt in g position : see below
2. lateral oblique (p.1446): pat ien t th ree-quarters oblique (alm ost pron e),
3. sem i-sit t in g
4. supin e w ith sh oulder roll, h ead alm ost h orizon tal
5. pron e
6. Con corde position : pron e, th orax elevated, n eck flexed an d t ilted aw ay from th e side on w h ich
th e surgeon w ill be stan ding
Sit t ing posit ion
Used less frequen tly th an in th e past because of associated com plicat ion s an d acceptable altern at ive
position s (except for som e specific circum stan ces). How ever, som e expert s feel th at th e risks of th e
sit tin g position h ave been greatly overstated.1
Advantages
1.
2.
3.
4.
im proved drain age of blood an d CSF out of surgical site
en h an ced ven ous drain age w h ich h elps reduce ven ous bleedin g an d also ICP
easy ven tilation due to un en cum bered ch est
patien t’s h ead m ay be kept exactly m idlin e, aidin g operator orien tation , an d reducin g risk of
kin kin g of vertebral arteries
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Disadvantages/risks
1.
2.
3.
possible air em bolism (see below )
fatigue of operators h an ds
in creased surgical risks from placem en t of CVP cath eter (required to treat possible AE): e.g.
pn eum oth orax w ith subclavian vein cath eterizat ion , th rom bosis
4. risk of post-op h em atom a at th e operat ive site m ay be in creased sin ce poten tial ven ous bleeders
m ay rem ain occult w h ile th e patien t is sitt in g, but m ay m an ifest w h en pat ien t return s to a h orizon tal position post-op. How ever, on e st udy foun d n o such in creased in ciden ce 2
5. risk of post-op subdural h em atom a: 1.3%of p -fossa cases 3
6. possible brach ial plexus injur y: preven t th is by n ot allow in g patien t’s arm s to h ang at th e side.
In stead, fold th em across abdom en
7. m idcervical quadriplegia 4,5: presum ably due to flexion myelopathy.6,7,8 The com bination of the sitting
position w ith hypotension 9 or neck flexion w ith possible com pression of the anterior spinal artery, ±
cervical bar, and elevation of the head thus reducing the arterial pressure m ay all contribute
8. sciatic n er ve injur y (piriform is syn drom e)10 : preven t th is by flexing patien t’s kn ees (reduces
ten sion on sciatic n er ve)
9. exten t of post-op pn eum oceph alus is m ore pron oun ced, an d m ay in crease th e risk of ten sion
pn eum oceph alus 11 ; see Pn eum oceph alus (p.887)
10. ven ous poolin g of blood in th e LEs un der an esth esia m ay cause relative hypovolem ia an d sh ould
be coun teracted by bin din g th e LEs prior to position in g
11. decreased cerebral blood flow due to low er h em odyn am ic arterial pressure 12
Air em bolism (AE): A poten tially fatal com plication of any operation w h en an open ing to air occurs
in a n on -collapsible vein (e.g. diploic vein or a dural sin us) w h en th ere is a n egative pressure in th e
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Procedures, Int ervent ions, Operat ions
vein (e.g. w h en th e h ead is elevated above th e h eart).13 Air is en train ed in th e vein an d can becom e
t rapped in th e righ t atrium of th e h ear t w h ich m ay im pair ven ous return causin g hypoten sion . May
also produce cardiac arrhyth m ias. Paradoxical air em bolism can occur in th e presen ce of a paten t
foram en ovale 14 or pulm on ary AV fistula, an d m ay produce isch em ic cerebral in farct ion .
Greater n egative pressures occur in th e sit t in g position due to th e extrem e elevation of th e h ead,
but AE can occur in any operation w ith th e h ead elevated h igh er th an th e h ear t. In ciden ce: a w ide
ran ge h as been quoted in th e literature, an d depen ds on th e m on itorin g m eth od used: ≈ 7–25% in ciden ce w ith th e sitt in g position usin g Doppler m on itoring is an estim ate.3
For operation s w ith a significa nt risk of AE, a righ t atrial CVP lin e is recom m en ded (to aspirate
air), an d m on itoring for air em bolism ; opt ion s in clude: tran sesoph ageal ech o (th e m ost sen sitive),
precordial Doppler m on itorin g. (Alth ough tech n ically th e risk of air em bolism in cludes a ny case
w here th e h ead is h igh er th an th e righ t cardiac atrium , pract ically it is lim ited to cases w h ere th e
h ead of th e bed is ≈ > 30° w h ich is m ostly lim ited to th e sit ting position for posterior fossa t um ors.)
Diagn osis an d t reatm en t:
AE sh ould be suspected in any operative case in w h ich th e surgical site is h igh er th an th e h eart
w hen th ere is any un explain ed hypoten sion or decrease in EtCO2 .16
● t ran sesoph ageal ech ocardiography (TEE). Bubbles can be seen on th e 2D ech o display
pros: con sidered th e m ost sen sitive m on itorin g m odalit y
con s: sign ifican t false positive rate, expen sive, invasive, requires experien ce an d vigilan ce
● precordial doppler U/S: probe m ay be placed over 2n d to 4th in tercostal space eith er to righ t or
left of stern um , or posteriorly bet w een th e scapula an d spin e. AE is h eralded by a ch ange in son ic
in ten sity an d ch aracter at first by a superim posed irregular h igh -pitch ed sw ish ing soun d, an d
th en as m ore air is en train ed so called “m ill w h eel” or m achin er y soun ds dom in ate
pros: th e m ost sen sitive of th e n on -invasive tech n iques
con s: di cult in m orbidly obese patien ts an d in certain pat ien t position s (e.g. pron e or lateral),
in terferen ce from oth er soun ds in th e OR, requires vigilan ce
The earliest in dication of AE m ay be a rise in th e en d-tidal n itrogen (requires m ass-spect rom eter on
m on itor), th en a fall in th e en d tidal pCO2 occurs. Mach in er y soun ds in th e precordial Doppler also
suggest AE. Hypoten sion m ay develop. Measures sh ow n in
Table 94.1 sh ould be im m ediately
in stituted.
Lat eral oblique posit ion
94
AKA “park ben ch” position .
● Axillar y roll for th e dow n side arm (see
Fig. 94.1) (or, position th e patien t so th at th e dow n side
arm exten ds over th e edge of th e table an d is h eld in place by a slin g form ed by th e Mayfield table
attach m en t w ith copious padding)
● Upper arm supported on pillow s or tow els (avoid using a Mayo stan d w h ich restricts th e abilit y to
laterally t ilt th e OR table during surger y)
● Adh esive tape to gen tly pull dow n on th e upper sh oulder
● Brin g th e patien t’s back as close to th e side edge of th e table as possible (usually lim ited by th e
t ravel of th e h ead clam p) to brin g th e pat ien t closer to th e surgeon
● Elevate th orax 10-15°
● Tilt th e vertex of th e h ead tow ards th e floor (see below )
● Option al spin al drain age (usually for large t um ors)
● Pillow betw een th e legs
● Secure patien t w ith adh esive tape over pads so th e table can be “airplan ed ” (rolled) durin g th e
operat ion
Table 94.1 Treatm ent for air embolism
1. find and occlude site of air entry, or else rapidly pack wound with sopping wet sponges/laps and wax bone
edges
2. lower patient’s head if at all possible (30° or less from horizontal)
3. jugular venous com pression (bilateral best; second choice: right only)
4. rotate patient LEFT side down (at tem pt to trap air in right atrium)
5. aspirate air from right atrium via CVP catheter
6. ventilate patient with 100% O2
7. discontinue nitrous oxide if used (m ay expand AE)15
8. use pressors and volum e expanders to maintain BP
9. PEEP is ineffective in preventing or treating AE; m ay increase the risk of paradoxical AE13
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Specific Craniot om ies
shoulder optional
tape
lumbar
drain
1447
stabilizing
tape (over
pads)
pillow between
the legs
axillary
roll
10-15 °
Fig. 94.1 Lateral oblique (“park bench”) position
30°
Fig. 94.2 Position of head and headholder
for right suboccipital craniectomy (looking
down on top of patient’s head)
©2001 Ma rk S Gre e nbe rg, M.D.
All rights re s e rve d.
Una uthorize d us e is prohibite d.
For access to the porus acusticus or m ore caudally
(e.g. for vestibular sch wan n om as; n ot n ecessary for m icrovascular decom pression for trigem in al
n euralgia).
Get th e sh oulders out of th e w ay by flexin g th e n eck as m uch as possible w h ile m ain tain in g paten t airw ay (aided by use of n on -kin king w ire-rein forced ET tube, so-called “arm ored t u be”). Th e
upper sh oulder is retracted caudally by adh esive tape (avoid excess t ract ion w h ich m ay injure brach ial plexus).
Head positioning
A Mayfield h ead-clam p is placed w ith th e sin gle pin on th e side of th e lesion , sligh tly an terior to a
t rue-lateral on th e sku ll ( Fig. 94.2.). Th e h ead is th en rotated 20–30° face-dow n from th e
h orizon tal.
94.1.3 Param edian suboccipit al craniect om y
Indicat ions
1. access to th e cerebellopon tin e an gle (CPA)
a) CPA t um ors, in cludin g:
● vestibular sch w an n om a
● CPA m en in giom a
● epiderm oid
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Procedures, Int ervent ions, Operat ions
b) m icrovascular decom pression
● trigem in al n euralgia
● h em ifacial spasm
● m iscellan eous: gen iculate n euralgia, glossoph ar yn geal n euralgia
2. lesions of on e cerebellar h em isph ere:
a) t um ors: m etastases, h em angioblastom as…
b) h em orrh age w ith in cerebellar h em isph ere
3. access to vertebral artery
a) aneur ysm s: PICA, vertebrobasilar jun ct ion
b) vertebral en darterectom y
4. access to an tero-lateral brain stem tum ors (extrem e lateral p -fossa approach )
a) foram en m agn um t um ors, in cludin g: ch ordom as, m en ingiom as
Posit ion, skin incision, craniect om y, approach…
See list of altern at ives (p. 1445). See lateral oblique position (p. 1446).
Skin incision
Linear (param edian) incisions
Access to CPA. For m icrovascular decom pression s an d sma ll CPA tum ors, a lin ear in cision provides
adequate exposure an d involves less t raum a to overlying m uscles, an d m ay be easier to get w atert igh t closure th an w ith m idlin e in cision . For all of th e follow in g, th e lin ear skin in cision is located
5 m m m edial to th e m astoid n otch (a palpable lan dm ark, Fig. 94.3):
1. “5–6-4” in cision (in cision placed 5 m m m edial to m astoid n otch , exten din g from 6 cm above
n otch to 4 cm below ). High en ough to expose t ran sverse sin us:
a) for approach to fifth n er ve: m icrovascular decom pression for t rigem in al n euralgia
2. “5–5-5” in cision (5 m m m edial, exten din g 5 cm up to 5 cm dow n ), used for approach to seven th /
eigh th n er ve com plex:
a) m icrovascular decom pression for h em ifacial spasm
b) sm all vest ibular sch wan n om a
3. “5–4-6” in cision (5 m m m edial, exten din g 4 cm up to 6 cm dow n ): used for approach to low er
cran ial n er ves:
a) glossoph ar yn geal n euralgia
“Hockey-stick” incision
94
Useful for cerebellar h em isph eric lesion s as w ell as for larger CPA lesion s w h ere getting th e m uscles
out of th e w ay w ill facilitate m an euverin g in st rum en ts about th e posterior fossa.
In cision is m ade in th e m idlin e startin g at ≈ C2 spin ous process, proceedin g superiorly to just
above th e in ion , an d th en laterally to just beyon d th e m astoid t ip ( Fig. 94.4). A sh ort option al caudal cur ve m ay be m ade laterally to furth er rem ove th e m uscle from th e operat ive field.
Craniect om y
Landm arks
Th e locat ion of th e in ferior m argin of th e t ran sverse sin us is quite accurately estim ated at t w o fin ger-breadth s above th e upper lim it of th e m astoid n otch (usually just above th e superior n uch al
lin e). Th is sh ould be th e upper lim it of th e sku ll open in g.
For m icrovascular decom pression
Cran iectom y ≈ 2 cm diam eter placed in th e an gle betw een tran sverse an d sigm oid sin uses.
For sm all tum ors (< 2.5 cm )
Cran iectom y ≈ 4 cm diam eter placed in th e an gle betw een tran sverse an d sigm oid sin uses.
For large tum ors
A larger cran iectom y m ay be n eeded, th e size of w h ich is lim ited by:
1. tran sverse sin us superiorly
2. foram en m agn um in feriorly (w h ich m ay be open ed as prophylaxis again st ton sillar h ern iation in
th e even t of p -fossa edem a post-op)
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mastoid process
sigmoid sinus
mastoid notch
linear skin incision
craniectomy
inion
"Frazier Burr Hole"
for ventriculostomy
(see text)
superior
nuchal line
transverse sinuses
Fig. 94.3 Param edian suboccipital craniectomy
94
"hockey stick"
incision
Fig. 94.4 “Hockey-stick” skin incision
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Procedures, Int ervent ions, Operat ions
3. sigm oid sin us laterally (open ing m astoid air cells is acceptable, but to preven t CSF leak, th ese
m ust be packed w ith bon e w ax an d m uscle (or bon e dust from cran iectom y 17 ), an d m ay be covered w ith reflected dura or fascia)
4. m idlin e m edially (un less th e tum or exten ds across th e m idlin e)
For approach to lower cranial nerves
(e.g. for glossoph ar yn geal n euralgia).
Cran iectom y is exten ded in feriorly to ≈ 1/2 cm above foram en m agn um .
Burr hole for em ergency ventriculost om y
Option ally placed prophylact ic occipital burr h ole (Fr azier bu r r h ole) usually for in traparen chym al
cerebellar tum ors or any situation w h ere post-op sw ellin g or hydroceph alus is likely (n ot com m on ly
used for m icrovascular decom pression or sm all vestibular sch wan n om as).
Location : 3–4 cm from m idlin e. In adults, 6–7 cm above th e in ion 18 ; in pediatrics, 2–3 cm above
th e tran sverse sin us 19 (p 429) (i.e. ≈ 3–4 cm above th e in ion ).
See Post-op m an agem en t (p. 1451) for use.
Approach t o t he CPA
Th e an gle of approach determ in es w h ich portion of th e posterior fossa is visualized.
1. retract in g th e cerebellum inferiorly (w orking in th e jun ction of th e ten torium an d petrous bon e)
gives access to th e region of th e t rigem in al n er ve, e.g. for m icrovascular decom pression for t rigem in al n euralgia
2. media l retract ion gain s access to th e region of th e porus acusticus, e.g. for vestibular
sch w an n om as
3. super ior retract ion gain s access to th e low er cran ial n er ves, e.g. for gen iculate n euralgia
94.1.4 Midline suboccipit al craniect om y
Indicat ions
94
Access to th e m idlin e or both sides of th e posterior fossa
1. m idlin e posterior fossa lesion s
a) cerebellar verm ian an d paraverm ian lesion s, in cludin g: verm ian AVM, cerebellar ast rocytom a
n ear th e m idlin e
b) t um ors of th e fourth ven tr icle: epen dym om a, m edulloblastom a
c) pin eal region t um ors
d) brain stem lesion s: brain stem vascular lesion s (e.g. cavern ous an giom a)
2. decom pressive cran iectom ies
a) for Ch iari m alform ation
3. cerebellar tum ors: m etastases, h em angioblastom a, pilocyt ic ast rocytom a…
Posit ion, skin incision, craniect om y, approach…
See position in g (p. 1446).
Skin/fascia incision
Midlin e in cision from ≈ 6 cm above in ion to ≈ C2 spin ous process. Take th e in cision a little h igh er if a
Frazier burr h ole is to be don e (can th en utilize th e sam e skin in cision ). Th e skin in cision sh ould
leave th e m uscles an d fascia in tact . It is often di cult to place Ran ey clips on th e skin in th is region .
To facilitate w ater-tigh t closure, th e fascia is “T’d” at th e top, leavin g a cu of t issue on th e occiput
just above th e superior n uch al lin e.
Craniect om y
Cran iectom y im plies rem oval of bon e (often piecem eal) w ith n o in ten tion of replacing it . Alth ough
cran iotom y w ith replacem en t of bon e flap at en d of procedure h as been used successfully, th ere is
som e con cern th at if th ere is post-op sw ellin g, th e in elastic bon e flap m ay cause m ore pressure to be
t ran sm itted to th e brain stem .
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Usually taken dow n to foram en m agn um . For cerebellar h em isphere t um ors, m any rem ove th e
posterior arch of C1 (caut ion re vertebral arteries on superior aspect of C1).
Approach
A “Y” sh aped durotom y is often used. If th e lesion h as a cystic com pon en t, aspiration th rough a ven tricular n eedle is used to par t ially decom press it .
94.1.5 Ext rem e lat eral post erior fossa approach
Allow s access to an tero-lateral region of brain stem . Di ers from above in th at th e skin in cision is
design ed to get th e bulk of th e skin an d m uscle flap out of th e w ay.
Key: rem ove th e lip of th e foram en m agn um as far laterally as possible, best don e w ith a diam on d
drill.
94.1.6 Cranioplast y for suboccipit al craniect om y
Methylm eth acr ylate cran ioplast y as part of th e closure follow in g suboccipital cran i for vestibular
sch w an n om a reduced th e in ciden ce of post-op H/A from 17%to 4%.20
94.1.7 Post -op considerat ions for p -fossa cranis
Post -op check
In
1.
2.
3.
addition to routin e, th e follow in g sh ould be ch ecked:
respiration s: rate, pattern (see In tu bation below )
follow closely for hyperten sion (see below )
evidence of CSF leak th rough w oun d
Post -op m anagem ent
Intubation
Post-op in tubation for 24–48 h ours is som etim es m ain tain ed on a precaution ar y basis: m any com plication s often h ave respirator y arrest as th e in itial m an ifestat ion (see below ), an d th e pat ien t m ay
deteriorate precipitously from th is poin t. Th ere is a t rade-o as th e st im ulus of th e en dotrach eal
tube m ay exacerbate hyperten sion an d patien t agitation , an d so sedation is often required, w h ich
m ay obscure th e n euro exam an d depress respiration s. If th e patien t w akes up extrem ely w ell from
an un com plicated p -fossa cran i an d it is n ot late at n igh t, m ost surgeon s w ill extubate.
Hypertension
Hyperten sion sh ould be avoided at all costs to preven t bleedin g from ten uous vessels (e.g. n itroprusside sh ould be prepared prior to term in ation of th e operation , an d sh ould be h an ging an d ready to
t it rate to keep SBP ≥ 160 m m Hg during th e reversal of an esth esia an d post-op).
Physician sh ould be called for any sudden ch anges in BP post-op (m ay in dicate elevated pressure
in posterior fossa, see below ).
Post -op com plicat ions
Posterior fossa edem a and/or hem atom a
In th e posterior fossa, a sm all am oun t of m ass e ect can be rapidly fatal due to th e paucit y of room
an d th e im m ediate tran sm ission of pressure directly to th e brain stem . It can also occlude CSF circulation th rough th e aqueduct an d cause a cute hydrocepha lus w ith th e atten dan t risk of ton sillar h ern iation . In creased pressure in th e p -fossa is usually h eralded by sudden in creases in BP or ch anges in
respirator y pattern (pupillar y reflexes, level of con sciousn ess an d ICP are not a ected un til late). See
Table 94.2 for em ergen cy treatm en t m easures.
Table 94.2 Emergency treatment for p-fossa swelling
Rapid intubation, ventricular tap (through previously placed burr hole, if possible, see below), and reoperation
is indicated. The wound should be opened im mediately wherever patient is (recovery room, ICU, floor…). CT
scanning m ay cost valuable m inutes; it is rarely appropriate to delay treatm ent for this (must be judged on an
individual basis).
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To expedite ven tricular taps, a prophylactic occipital burr h ole (Frazier burr h ole) is often placed
durin g posterior fossa surgery to perm it drain age of CSF from th e lateral ven tr icles in th e even t of
acute hydrocephalus from blockage of th e 4th ven tr icle or aqueduct . If acute hydroceph alus develops
(e.g. from a h em atom a), an em ergen t percutan eous ven t ricular tap w ith ven tricular n eedle (or, if n ot
available, spin al n eedle) is perform ed, passing th e n eedle th rough th e burr h ole aim in g for th e m iddle of th e foreh ead. In th e presen ce of acute hydroceph alus, CSF sh ould be en coun tered at a depth of
3–5 cm . NB: th is m an euver m ay provide a few m ore m in utes w h ile preparin g for th e defin itive t reatm en t of re-open ing th e w oun d; h ow ever, hydroceph alus m ay n ot in itially be presen t sin ce it takes
som e t im e to develop.
Suboccipital pseudom eningocele
An “in tern al” CSF fist ula. In ciden ce follow in g suboccipital cran iectom y: 8 21 -28%.22
May be asym ptom atic, but also m ay be associated w ith H/A, n ausea/vom itin g, local pain /ten dern ess. Som e are soft an d com pressible, oth ers m ay be tense.
In dication s for operation :
1. extern al leak (CSF fistula, see below )
2. th reaten in g in tegrit y of in cision
3. cosm etic deform it y
4. causin g sym ptom s
Treatm en t option s (up to 67% require perm an en t CSF drain age 23 ):
1. n on invasive m easures: expectan t m an agem en t, fluid restriction , h ead w rapping, keeping HOB
elevated, acetazolam ide. Steroids m ay be used if aseptic m en ingitis is suspected
2. percutan eous aspiration : “tap an d w rap”.19 (p 436),24 Risks in t roducing bacteria, causin g in fect ion
3. direct surgical exploration w ith m ultilayer re-closure 19 (p 436)
4. lum bar drain : e ect ive on ly if pseudom en ingocele com m un icates w ith th e subarach noid space.
May produce acute posterior fossa syn drom e (H/A, n ausea, vom it in g, ataxia…) 21 especially if
th e pseudom en ingocele doesn’t com m un icate. Sym ptom s usually resolve w ith prom pt discon tin uation of lum bar drain age.21,22 Oth er poten tial com plicat ion s: vagal n er ve palsy, ton sillar h ern iation , subdural h em atom a, kin kin g of PCA → st roke. Drain age option s:
a) extern al drain (tem porar y)
b) lum boperiton eal sh un t (perm an en t)
5. ven tr icular drain age
a) EVD (tem porar y)
b) sh un t (perm an en t)
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CSF fistula
Occurs in 5–17% of cases. A poten tial source of m en in gitis, th us CSF leak m ust be t reated
im m ediately.
Etiologies: con troversial. May in clude:
1. abn orm al CSF hydrodyn am ics (i.e. hydroceph alus). Man euvers to stem th e leak w ill likely fail
un til th e CSF is sh un ted or hydrodyn am ics n orm alize
2. poor w oun d closure: probably blam ed m ore often th an it is th e actual cause
3. subarach noid scarr ing
May be associated w ith m en in gitis (aseptic or in fect ious), m ultiple operation s. Form ation m ay be
facilitated by cough ing/sn eezin g, post ural ch anges, on e-way ball-valve m ech anism due to a tissue
flap.
An extern al CSF leak m ay occur th rough :
1. th e skin in cision
2. via th e eustach ian tube; see possible routes of egress follow in g suboccipital vestibular sch wan n om a rem oval (p. 683):
a) th rough th e n ose (CSF rh in orrh ea)
b) dow n th e back of th e th roat
3. th e ear (CSF otorrh ea) in cases w ith perforated TM
Treatm en t:
In itial treatm en t m easures to tem porize in th e h ope th at CSF hydrodyn am ics w ill n orm alize an d/
or th at th e leak site w ill scar closed w ith in a few days:
1. elevate th e HOB
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2. lum bar subarachn oid drain age
3. if th e leak occurs th rough th e skin in cision :
a) rein force th e in cision w ith sut ures, e.g. run n ing locked 3–0 nylon after preparation of th e skin
w ith an tim icrobial an d local an esth etic
b) altern atively, th e in cision m ay be pain ted w ith several coats of collodion
If persisten t, a CSF fistula requires surgical correction , see CSF fistula (cran ial), for gen eral in form at ion (p.384), see CSF fistula follow in g suboccipital rem oval of vestibular sch wan n om a (p. 684).
Fifth or seventh nerve injuries
Causes dim in ish ed corn eal reflex w ith poten tial corn eal ulcerat ion ; in itially m an aged w ith isoton ic
eye drops (e.g. Natural Tears®) q 2–4 h rs & PRN, or w ith a m oist urizin g in sert (e.g. Lacricert ®) q day,
an d at n igh t w ith an eye patch or taping eyelid sh ut.
Miscellaneous
Supraten torial in tracerebral h em orrh age h as been described, an d m ay result from t ran sien t
hyper ten sion .25
94.2 Pt erional craniot om y
94.2.1 Indicat ions
1. an eur ysm s
a) all an eur ysm s of an terior circulation
b) basilar t ip an eur ysm s
2. direct surgical approach to cavern ous sin us
3. suprasellar t um ors
a) pit uitary aden om a (w h en th ere is a large suprasellar com pon en t)
b) cran ioph ar yn giom a
94.2.2 Technique
Posit ion, skin incision, craniect om y, approach…
1.
2.
3.
4.
supin e, ipsilateral sh oulder roll if h ead t urn ed > 30° (see below )
elevate th orax 10–15°: reduces ven ous disten sion
flex kn ees
Mayfield 3 pin h ead-h older: applied betw een t rue AP an d true lateral (so th at it is ≈ h orizon tal
w h en h ead is rotated to th e n ecessary position , see Fig. 94.5)
5. n eck exten ded 15°: allow s gravity to retract fron tal lobe aw ay from sku ll base
6. h ead rotated from ver tical as sh ow n in Fig. 94.5
Room arrangem ent
1. m icroscope: obser ver tube to operator’s right for eith er righ t or left pterion al cran i
Skin incision
See Fig. 94.6. From zygom atic arch 1 cm in fron t of t ragus (to avoid fron talis bran ch of facial n er ve
an d fron tal bran ch of superficial tem poral artery), cur vin g sligh tly an teriorly, staying beh in d h airlin e
to w idow ’s peak, option al addit ion al cur ve beyon d m idlin e to aid in skin retract ion . Over tem poralis
m uscle, in cise skin dow n to but n ot th rough tem poralis fascia.
Th e tem poralis m uscle m ay be in cised caudal to th e skin in cision (i.e. closer to zygom at ic arch ):
th is m in im izes th e m uscle m ass th at n eeds to be retracted in feriorly an d yet keeps th e scar beh in d
h airlin e (n ote: th ere is an in creased risk of fron talis w eakn ess w ith th is tech n ique th an if th e tem poralis m uscle is in cised in -lin e w ith th e skin in cision ).
Craniot om y
Th ere are n um erous w ays to cross th e pterion (th e lesser w in g of th e sph en oid m akes th is di cult).
On e m eth od is outlin ed h ere, Fig. 94.7.
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