Outline of
Neurosurgery
E.R. Flotte, 2008
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and corrections to admin@flotte2.com
Head Circumference: Neonate: 1cm/wk; 1-3m: 2cm/wk; 4-6mo: 1cm/mo;
6-12mo: 0.5cm/wk
Craniosynostosis
·
Types
o
Sagittal: scaphocephaly
(most common)
o
Coronal: causes “harlequin eye”
o
Lambdoid
o
Metopic
(frontal): trigonocephaly.
o
Oxycephaly, turricephaly, acrocephaly: lambdoid and coronal (cone head, oxycepaly
= pointed, turricephaly = flat forehead).
o
Klebblatschadel
(Clover-Leaf): all sutures except squamosal.
o
Nonsynostotic scaphocephaly: “sticky sagittal suture” (JN:P 8/04)
·
Causes increased ICP in 11%.
·
Ridge often forms over synostosis
·
Diagnosis:
·
Treatment: Surgery – for cosmesis
& brain development. Craniectomy with reconstruction (often with plastic
surgeon). Generally done 3-12 months old.
·
“Lazy Lambdoid”: positional
occipital flattening, mimics synostosis.
Treated by repositioning (eg prone) or molding
helmets
Encephalocoele
·
Occipital
= whites, Frontal (sincipital, frontoethmoidal)
= asians. Also: parietal, transphenoidal, nasal (assoc. with nasal gliomas – dysplastic tissue).
·
50%
develop hydrocephalus within 1mo.
·
Meckels syndrome: encephalocoele + dysplastic kidneys, cardiac probs,
facial clefts.
·
Treatment:
surgical excision & dural closure. Nasal:
combined transcranial and transnasal
approach.
Spinal Dysraphisms
Myelomeningocoele
·
Due to defect in primary neurulation
(3-4 weeks). Covered by thin membrane.
·
Almost all patients have associated Chiari II
malformation
·
Risk factors: Maternal low folate,
valproate, Tegretol. 3%
risk on subsequent births.
·
Prevention: Folate
supplementation (0.4mg/day) from 1 month before pregnancy to end of 1st
trimester.
·
Diagnosis: maternal serum AFP > amniocentesis AFP & acetylcholinesterase (peaks 12-14wks).
·
Complications: Tethered cord, Chiari II, syrinx, hydrocephalus. 80% have normal IQ.
o
With neurologic deterioration always check for shunt
malfunction first.
o
Urology, orthopedic consults needed. Bladder
catheterization.
·
Treatment:
If ruptured start antibiotics and cover defect. Antibiotics if
unruptured is controversial
o
Close MM within 24hrs whether open or not. Decreases infection, doesn’t change function.
o
Controversial whether to wait >3d after closure
before shunting or perform it simultaneously.
·
Closure:
o
Avoid contacting placode
with betadine or other solutions (general belief)
o
Oval incision around junction of placode
and intermediate zone (abnormal epidermis).
o
Avoid including epidermis with placode
– may for epidermoid, etc
o
Laminectomy of last normal level to identify normal dura.
o
Dissect dura around placode. Preserve nerve roots
o
Close placode, then dura.
o
Approximate lumbar fascia. Close skin – may need
undermining or flap (consider plastic surgery consult)
Occult
spinal dysraphisms (OSD)
·
Meningocoele, lipomyelomeningocoele, diastematomyelia,
fatty filum, etc. Defects of secondary neurulation.
·
Cutaneous abnormality: “Fawn’s tail”, lipoma,
dermal sinus tract, dimple, etc. May not correspond to level of dysraphism. Fawn’s tail very suggestive of diastematomyelia. Capillary hemangiomas
are normal near occiput, 10% OSD if thoracolumbar.
·
In general not associated with brain abnormalities.
·
Maternal AFP not elevated. Dx:
MRI +- xrays.
·
Consider intraop monitoring (cystometrogram,
bladder/ rectal EMG, nerve stimulation, EPs). If dura
is adherent posteriorly, excise dura
circumferentially.
Meningocoele
·
Usually neurologically normal, no associated
abnormalities. Rule out hydrocephalus.
·
May contain aberrant nerve roots/ gliotic
tissue. May occur off-midline.
·
Treatment: elective repair. Usually ends in
narrow neck.
·
Myelocystocoele = meningocoele
+ hydromyelia. Occurs with omphalocoele,
bladder exstrophy, imperforate
anus.
Lipomyelomeningocoele
·
AKA spinal lipoma of the conus (SLC).
·
Usually have cutaneous stigmata. Not associated with
Chiari II.
·
May be off midline (ipsilateral LE more affected),
contain CSF.
·
Dorsal insertion (type I): Nerve
roots lie ventral. Usually contiguous with subcutaneous fat.
·
Caudal (terminal) insertion (type III): Lipoma
either replaces filum or runs separately. Nerve roots
may run in lipoma. May be entirely intradural or from subcutaneous fat.
o
Some include transitional (type II): inserts on conus, no normal tissue below defect
o
Type I occur during primary neurulation,
III during secondary neurulation.
·
Can contain teratomas (i.e. bowel).
·
Symptoms: Usually normal in infancy. Causes
tethered cord - leg
pain, LE neurologic deficit.
·
Diagnosis: MRI.
·
Treatment:
o
Surgery if symptomatic, scoliosis etc.
o
Most recommend prophylactic surgery but is
controversial. Kulkarni (N4/04) showed deterioration
is higher for surgically treated patients than observed ones.
·
Surgery:
o
Midline incision (even if off midline). Follow thru fascial defect. Laminectomies, durotomy
1-2 levels above to find normal dura.
o
Untether cord
(check & section filum), remove lipoma as much as possible, close myeloschisis
if present (reduce retethering), reconstruct dura.
o
Dorsal: Can use laser to remove fat, close pia.
o
Caudally inserting: divided after take-off of last
normal root – unnecessary to remove all gross lipoma.
o
Use SSEP, nerve root stimulation
o
Keeping the patient prone postop may reduce CSF leak
and retethering(?)
o
“Only in the event of progressive neurologic
deterioration should one reuntether” – McComb.
Diastematomyelia
·
Lumbar > thoracic.
·
Cutaneous abnormality (75%) may not correspond to diastem. Fawn’s tail most common.
·
Clinically presents as tethered cord. Associated with scoliosis, myelomeningocoele, vertebral anamolies.
·
May consist of 1 or 2 dural
tubes; may have duplication of spinal cord (diplomyelia). Diastem may
incompletely span canal, may be dorsal or ventral; may not have bony diastem.
·
Treatment: Symptomatic: operate.
Asymptomatic: controversial. Some advocate operating before 2yo (bony diastem or not). Surgery mostly prophylactic, although some
improve.
·
Surgery: May have lipomatamous
filum - Remove septum before detethering. Closing anterior dura
not necessary. Elliptical dural incision made around
septum - cuff of dura left on seputm
base. May be aberrant nerve roots in midline near septum, can sacrifice.
Butterfly
vertebrae/ Hemivertebrae: may mimic
fracture
Occult spina bifida:
Anterior
sacral meningocoele
·
May contain neural elements or not. May present as pelvic mass, HA with
defecation. May complicate labor.
·
Asymptomatic may be followed if not enlarging, no
chance of pregnancy.
·
Symptomatic patients: surgery. L5-S4 laminectomy
performed. Ostium oversewn,
filum divided, pelvic mass not removed. If dural defect is wide can perform digital decompression thru
rectum or fascial graft. Aspiration thru rectum or
vagina should not be performed.
Dermal
sinus:
·
May end extradually or
extend intradurally. In cervical or thoracic spine it
can end in central canal. Lumbar can terminate in filum
or intradural dermoid cyst (may be in filum or intramedullary). May be associated with a lipoma.
·
May have purulent drainage. Can cause recurrent
meningitis.
·
Diagnosis: MRI
·
Sacral or coccygeal sinuses
don’t need to be explored, lumbar do. Probing and contrast injection may cause
meningitis. If extends to dura, open dura. Can require laminectomies to T12. If dermoid cyst has ruptured and scarred, or
is embedded within conus, avoid total removal – do intracapsular decompression.
Sacral
Agenesis
·
15% associated with maternal diabetes. Motor deficit
= lowest level with intact pedicles. Varies from coccygeal
to thoracic agenesis. Can be asymmetric. Neuro loss can be from minimal to
complete. Treatment: fusion
·
Caudal regression syndrome: Sacral
agenesis, imperforate anus, renal dysplasia, sirenomyelia. Also associated with VATER syndrome.
Myelocystocoele: see Muthukumar JN:P 8/07.
·
Terminal
myelocystoceles: 1) skin-covered lumbosacral
spina bifida; 2) meningocele;
and 3) low-lying hydromyelic spinal cord that
traverses the meningocele and then expands into a
large terminal cyst.
·
Nonterminal myelocystoceles are much less
common than terminal myelocystoceles and are
frequently misdiagnosed as meningoceles.
·
Excise
dilated cystic tissue, preserving anterior nerve roots
Sinus pericranii: Presents as scalp mass. Large subcutaneous venous sinus.
Dermoid
cyst: Inion is most likely site for
intracranial extension
Growing
skull fracture: 75% of patients are <1yo. Rare
>3yo. Requires >3mm diastasis to occur.
Cephalohematoma: subperiosteal, does not
cross sutures, Caput succedaneum in
subcutaneous fat, crosses sutures; Subgaleal hematoma;
all may cause significant blood loss, check Hct.
Arachnoid Cyst
·
Can occur anywhere.
Most common in middle fossa (seizures), suprasellar (visual loss,
precocious puberty, bobble-headed doll).
·
May present at any age
·
Symptoms: seizures, deficits, headache, visual
deficits, developmental delay, endocrinopathies. Can
rupture, cause hyperostosis or hydrocephalus.
·
Associated with intracystic
and subdural hemorrhage.
·
Natural history is variable: may enlarge, regress, or
remain static
Treatment
·
.Most recommend treating only if symptomatic
(intractable headaches, seizures, focal deficits) or increasing size
o
Needle/burrhole – most
recur
o
Craniotomy & fenestration: most effective if
fenestrated into basilar cisterns (2cm Microcraniotomy:
N11/03). Improves seizure control and focal deficits; visual disturbances,
developmental delay, and endocrinopathies persist.
o
Cystoperitoneal shunt:
usually if fenestration fails. Shunt dependency may develop.
o
All cases presenting with hydrocephalus required VP
shunting regardless whether fenestration was performed.
o
Endoscopic fenestration
o
Suprasellar: Transcallosal, ventriculocystostomy
(endoscopic). HCP may increase after
treatment. Concomitant hydrocephalus usually requires VP shunt. Subfrontal
fenestration not recommended.
·
Outcome: Improvement (keyhole crani)
hemiparesis & CN6 palsy 100%, headaches 66%,
seizures 50%.
Chiari I Malformation
·
3-5mm tonsillar herniation. Controversial whether degree of herniation correlates with symptoms
or postop improvement.
·
Headaches: classically occipital,
worsen w/Valsalva. Also cranial
nerve, brainstem & spinal cord syndromes. Downbeat
nystagmus.
·
60% have syringomyelia
(may be thoracic or lumbar); 25% hydrocephalus; 25% craniocervical
junction abnormalities; 20% scoliosis; 5% Klippel-Fiel,
5% GH deficency. Not associated with other developmental
brain abnormalities.
·
No recommendation for
participating in athletics.
·
Diagnosis: MRI. Obtain preop
flexion/extension c-spine xrays.
o
Cine-MRI may demonstrated
decreased CSF flow in the foramen magnum but predictive value is controversial.
·
Treatment
o
Asymptomatic: Decompress only for syrinx; if no
improvement then shunt. (But - Nishizawa (N01) 8/9 w/
syrinx remained asymptomatic.)
o
Symptomatic: If HCP: shunt. No HCP: decompression,
if fails then shunt syrinx.
o
Anterior
compression (VBSC): transoral odontoidectomy
BEFORE decompression.
o
Scoliosis:
improves with decompression; perform spinal fusion only for Cobb angle >50º.
(JN8/03)
o
Chiari Decompression: 3x3cm suboccipital craniectomy,
C1 (or lower) laminectomy, duraplasty, (some
cauterize tonsils). If extensive scarring can use ultrasound to find 4th
ventricle. Stenting worsens outcome. Postop: watch for sleep apnea. 50-85%
success. If has occipitalcervical instability, can do
concomitant OC stabilization (N6/04). Best if done within 2yrs of onset. SE: “cerebellar sag”: requires cranioplasty.
Chiari II
·
100% associated
with myelomeningocoele. 90% have hydrocephalus.
·
Treat
hydrocephalus with shunt 1st
· Decompress for apnea, stridor, dysphagia, progressive spasticity or ataxia, opisthotonus, recurrent aspiration pneumonia. Check shunt