Keywords
Chiari malformation type I - syrinx - foramen magnum decompression
Introduction
Chiari malformation (CM) type I are becoming more commonly faced by neurosurgeons
with increased uses of magnetic resonance imaging (MRI). This complex entity is a
collection of hindbrain abnormalities having long medical history. Several classic
reviews have been attempted to clarify a variety of complex associated issues. Despite
the volumes of publications on the subject, the literature review shows that the natural
history of this disease process has not been established. Abnormal cerebrospinal fluid
(CSF) dynamics across craniovertebral junction and frequent spinal cord cavitation
are among the prominent facets of disease process.
The clinical examination is crucial in the diagnosis, and the challenge is to identify
which patients will benefit most from posterior fossa decompression. Controversy regarding
operative intervention continues in patients without a syrinx, and surgical indications
may vary among surgeons, especially for subjective symptoms such as headache. Management
is further complicated by variability in technical aspects of decompression. In our
study, complete surgical experience of 74 patients who were operated upon for adult
presentation CM type I with syrinx was retrospectively analyzed. We set out to identify
important surgical implications that most likely benefit patients. By analyzing operative
intervention in patients with appropriate symptoms and then following their course,
we hope to outline the present status of this entity.
Subjects and Methods
This is a retrospectively analyzed study of 74 patients (mean age: 28.8 years, range:
6–58 years, 55 males and 19 females) who were managed surgically for adult CM type
I from 1998 to 2016. The inclusion criteria were symptomatic patients with appropriate
clinical findings and MRI consistent with CM type I. Patients included in this study
were followed in postoperative period for at least 18-month duration. Patients in
whom another cause was established (trauma, arachnoiditis, and tumor), atlantoaxial
dislocation, and those who lost follow-up were excluded from study. Control group
consisted of the patients with CM type I in long-term follow-up in outpatient department
(OPD) who opted for conservative management. Because of this, statistical comparison
was not possible between these two groups.
Pain in the suboccipital or cervical region was the predominating symptom in most
patients (56%). Average duration of symptoms clearly related to CM type I was 4.2
years (range: 2 months to 15 years). In current era of MRI, latency is reduced. The
clinical profile of patients is summarized in ([Table 1]). The radiologic investigations included MRI craniovertebral junction with screening
of the spine and dynamic computed tomography (CT) of the craniovertebral junction
in patients with evidence of skeletal anomalies on plain X-ray. The extent of tonsillar
herniation in relation to foramen magnum and atlas (C1) arch was meticulously measured
in millimeter in all cases along with screening for syrinx. There was associated syrinx
in 47 (64%) cases ([Fig. 1]). The rostrocaudal extent and maximum diameter of syrinx were clearly documented
on preoperative scans as a baseline for subsequent follow-up. The summary of radiologic
findings is presented in ([Table 2]).
Table 1
Presenting signs and symptoms of patients having Chiari malformation type I
|
Signs and symptoms
|
No. of cases
|
%
|
|
Suboccipital pain
|
42
|
56
|
|
Weakness
|
34
|
45
|
|
Hand atrophy
|
26
|
35
|
|
Spasticity
|
24
|
32
|
|
Hyperactive deep tendon reflexes
|
32
|
43
|
|
Numbness (≥ 1 limbs)
|
32
|
43
|
|
Loss of temperature sensation
|
30
|
39
|
|
Posterior column loss
|
24
|
31
|
|
Facial numbness
|
2
|
3
|
|
Unsteadiness
|
30
|
40
|
|
Nystagmus
|
35
|
47
|
|
Tinnitus
|
5
|
7
|
|
Deafness
|
2
|
3
|
|
Cerebellar signs
|
20
|
27
|
|
Horner's sign
|
5
|
6
|
Fig. 1 Magnetic resonance imaging (MRI) of the spine showing Chiari malformation type I
with syrinx formation in cervical cord in (a) T2- and (b) T1-weighted sequence.
Table 2
Radiologic details of Chiari malformation type I and associated bony anomalies
|
Radiologic features
|
No. of cases
|
%
|
|
Tonsillar herniation
|
|
|
|
Foramen magnum
|
5
|
6
|
|
C1 arch
|
31
|
42
|
|
C2 lamina
|
27
|
36
|
|
C3 lamina and below
|
11
|
16
|
|
Skeletal anomalies
|
|
|
|
Basilar invagination
|
18
|
25
|
|
Atlanto–occipital assimilation
|
15
|
20
|
|
Fused cervical vertebrae
|
9
|
12
|
|
Syringomyelia
(Cine–mode magnetic resonance imaging)
|
47
|
64
|
Surgical management was standard foramen magnum decompression with C1 arch removal
and partial axis (C2) laminectomy, depending on extent of tonsillar descent in all
the cases ([Fig. 2]). A wide pericranial graft was routinely harvested from occipital region in all
the cases. Intradural manipulation was individualized in form of adhesiolysis (16%)
extrapial coagulation of tonsillar tip (13%), and in early phase of study plugging
of obex (4%) was also performed. Augmentation duraplasty was done using either pericranial
graft (83%) or synthetic graft (8%) ([Fig. 3]). Fibrin glue reinforcement of suture line was done in 62% patients. Intervention
for syrinx without craniovertebral decompression in form of syringostomy (two patients)
and syringoplural shunt (two patients) was done in early phase of study. The surgical
procedures performed are summarized in ([Table 3]). The outcome analysis was based on postoperative clinical improvement and reduction
in diameter of syrinx on postoperative MRI and categorized into improved, unchanged,
or worsened.
Fig. 2 Exposure after standard foramen magnum decompression, atlas posterior arch removal,
and partial axis (C2) laminectomy, depending on extent of tonsillar descent in MRI
of the spine.
Fig. 3 Augmentation duraplasty using pericranial patch after bony bridge decompression.
Table 3
Surgical details
|
Surgical Methods
|
No. of cases
|
%
|
|
Foramen magnum decompression
|
|
|
|
Suboccipital craniectomy
|
70
|
95
|
|
C1 laminectomy
|
42
|
55
|
|
C2 partial laminectomy
|
15
|
20
|
|
Intradural exploration
|
|
|
|
Adhesiolysis
|
12
|
16
|
|
Extrapial coagulation of tonsillar tips
|
10
|
13
|
|
Plugging of obex
|
3
|
4
|
|
Duraplasty
|
|
|
|
Pericranial graft
|
64
|
83
|
|
Synthetic graft
|
6
|
8
|
|
Reinforcement by fibrin glue
|
48
|
62
|
|
Intervention for syrinx
|
|
|
|
Syringostomy
|
2
|
3
|
|
Syringoplural shunt
|
2
|
3
|
Results
Out of 74 patients included in study, mean age was 28.8 years (range: 6–58 years).
The majority of the included patients were in second or third decades (43%), with
male preponderance (55 males and 19 females). Average duration of symptoms clearly
related to CM type I was 4.2 years (range: 2 months to 15 years). In our study, no
definite pattern of progression in natural history of disease was noted. Most of the
patients who were symptomatically stable for months to years presented with recent
rapid progression. The most common symptom was suboccipital pain, brought on by neck
movements or Valsalva's maneuver. Ten patients had headache as the only complaint,
and one-half of the patients were initially labeled as functional. The most common
finding included lower extremity weakness, hyperreflexia, and spasticity with atrophy
in upper extremities ([Fig. 4]). More than one-third of patients had sensory abnormalities in the form of decreased
pain and temperature sensation in the upper limb and decreased proprioception in the
lower limb. Nystagmus was present in 35 (47%) patients, which was of downbeat type.
Other cerebellar signs were present in 20 (27%) patients and Horner's sign in 5 (6%)
patients. Cranial nerve involvement in form of facial numbness was present in two
(3%) patients, tinnitus in five (6%), and deafness in two (3%) patients.
Fig. 4 Clinical photograph of hand muscle atrophy in Chiari malformation type I with syrinx.
On the basis of clinical presentation, patients were divided into three categories:
foramen magnum compression syndrome (suboccipital pain, weakness, spasticity, hand
atrophy, hyperactive deep tendon reflexes, facial numbness, and Horner's syndrome
as predominant presenting features), central cord syndrome (dissociative sensory loss,
segmental lower motor weakness in upper extremity, and long tract signs), and cerebellar
syndrome (unsteadiness, nystagmus, and other cerebellar signs). Most patients in our
study fall in the category of foramen magnum compression syndrome. MRI study showed
tonsillar descent up to C1 arch in 31 (42%) patients, C2 lamina in 27 (36%), and subaxial
spine (C3) or below in 11 (16%) patients. The tonsillar descent was meticulously calculated
in millimeter in all the cases. There was associated syringomyelia in 47 (64%) patients,
principally in the cervical cord. Entire rostrocaudal extent of syrinx was analyzed.
Maximum diameter in millimeter was measured and documented as baseline for objective
assessment of improvement in postoperative follow-up period. Associated bony anomalies
such as basilar invagination, atlanto-occipital assimilation, and fusion of the cervical
vertebrae were seen in 20 (27%) patients. In all these subset of patients, dynamic
CT of the craniovertebral junction was done to rule out atlantoaxial dislocation ([Fig. 5a, b]). Foramen magnum decompression with C1 arch removal and partial C2 laminectomy depending
on extent of tonsillar descent was done in most patients. The extent of suboccipital
craniectomy was up to medial margins of occipital condyles in the initial phase of
this study, followed by suboccipital craniectomy limited to decompression of entire
posterior surface of tonsils in the recent phase of this study ([Figs. 6], [7]). The dense constrictive band causing intradural constriction was seen in 22 (30%)
patients in whom intradural exploration was done ([Figs. 6], [8]). Adhesiolysis was done in 12 (16%) patients. In severe tonsillar ectopia occluding
the foramen of Magendie, extrapial coagulation of tonsillar tip was done in 10 (13%)
patients. In nine (12%) patients, a thin membrane was found covering the obex that
on piercing. free flow of CSF was established. In all cases of intradural manipulation,
choroid plexus in the fourth ventricle was visualized, and free flow of CSF into subarachnoid
space was ensured. In the early phase of this study, in three (4%) patients, an occluding
muscle plug was placed in dilated central canal at the obex to interrupt its hydrodynamic
continuity with the fourth ventricle. This obex plugging procedure was abandoned later
due to more neurologic complications and change in concept of syrinx pathophysiology.
Augmentation duraplasty with autologous pericranial graft was done in 64 (83%) patients,
and synthetic graft in 6 (8%) patients. Reinforcement of suture line with fibrin glue
was performed in 48 (62%) patients. Intervention for syrinx was done in four (6%)
patients ([Table 4]). Postoperative complications included CSF leak in nine patients and wound infection
in three patients, which were tackled with uneventful recovery. With the experience
of previous decompressive procedures addressing to basic pathophysiology of CSF dynamics
in syringomyelia, surgical strategy evolved from more aggressive approach into simpler
and least invasive approach in the recent study. At 6-month follow-up, 42 patients
had improvement, and 19 had stabilization in clinical course with worsening of symptoms
seen in 13 patients ([Table 5]). Significant improvement was seen in foramen magnum compression syndrome group.
Follow-up MRI of the cervical spine in these patients showed marked reduction in syrinx
size and well-decompressed foramen magnum with adequate CSF space around the cervicomedullary
junction as compared with preoperative MRI ([Figs. 9], [10]).
Fig. 5 (a, b) Dynamic computed tomography scan of craniovertebral junction to rule out bony instability
in Chiari malformation type I with syrinx.
Fig. 6 Intraoperative image showing thickened dural ligamentous complex at the level of
craniovertebral junction causing compression in Chiari malformation type I.
Fig. 7 Intraoperative images showing (a) dural incision line across the craniovertebral junction (in green) and (b) exposure of both tonsils beyond foramen magnum and arachnoid band for adhesiolysis.
Fig. 8 Intraoperative image showing cutting of dural-ligamentous complex band at the level
of craniovertebral junction.
Fig. 9 Comparative MRI sagittal image of the cervical spine. (a) Preoperative and (b) follow-up at 6 months showing adequate foramen magnum decompression and continuation
of craniospinal CSF space all around the cervicomedullary junction as well as marked
reduction in syrinx diameter size.
Fig. 10 Comparative MRI axial image of the cervical spine. (a, b) Preoperative and (c, d) follow-up at 6 months showing adequate foramen magnum decompression and continuation
of craniospinal CSF space all around the cervicomedullary junction as well as marked
reduction in syrinx diameter size.
Table 4
Surgical outcome at 6 months of follow–up
|
Surgical procedure
|
Total
|
Better
|
Worse
|
No change
|
|
1. Foramen magnum decompression with duraplasty
|
58
|
35
|
9
|
14
|
|
2. Foramen magnum decompression with intradural exploration and duraplasty
|
12
|
6
|
4
|
2
|
|
3. Intervention for syrinx
|
4
|
1
|
0
|
3
|
Table 5
Outcome in long–term follow–up of 74 cases grouped in categories
|
Outcome
|
Foramen magnum compression group
|
Central cord syndrome group
|
Cerebellar syndrome group
|
|
Improved
|
31
|
5
|
6
|
|
Unchanged
|
3
|
12
|
4
|
|
Worse
|
4
|
6
|
3
|
|
Total
|
38
|
23
|
13
|
Many patients in our study who initially improved with surgery frequently returned
to their presurgical state or sometimes even became worse and continued to deteriorate.
Whether this denotes the natural course of the condition in a subset of this patient
population is not known. In our study an attempt is done to overcome this bias by
analyzing patients with CM type I who opted for conservative management as control
group. This comparative analysis, unique in our study, is instrumental to ascertain
the true benefits of surgery over what may be the natural history of this condition.
Discussion
The natural history of syringomyelia varies from spontaneous and complete regression
to progressive neurologic deficits rightly described as “relentlessly progressive”
by Lord Brain.[1] The unpredictable clinical course of syringomyelia causes difficulties and controversies
regarding management and continues to pose challenges. There is no currently clear
consensus about the optimal therapy, and differing opinions are found in the literature.
Another problem, encountered in interpreting the available information, is that a
fairly long follow-up is required because syrinx progression may occur slowly over
time. However, there is no effective nonsurgical alternative to operative decompression
for patients with symptomatic CM type I. The detailed understanding of the underlying
pathophysiologic mechanisms is required to identify which patients will benefit most
from posterior fossa decompression.
Pathophysiologic Basis of Clinical Manifestations of Disease
The CM type I consists of caudal displacement of cerebellar tonsils into the upper
cervical canal, causing direct compression of the cerebellum or medulla at foramen
magnum, which was the basis of suboccipital headache and neurologic signs and symptoms
arising from the cerebellum and medulla. The full foramen magnum potentially compresses
the herniated cerebellar tissue and restricts normal CSF flow across the craniovertebral
junction, which increases the CSF movement in the spinal canal resulting in syrinx
formation. The spinal cord damage starts centrally and spreads centrifugally to involve
other spinal cord structures. Characteristically, the decussating fibers of spinothalamic
tract conveying pain and temperature sensation are compromised initially. This results
in loss of pain and temperature in “vest like” bilateral distribution with the preservation
of soft touch sensation and proprioception, characteristically described as dissociation
of sensory loss. With forward extension of disease process, the anterior horn cells
become involved at the level of lesion resulting in segmental lower motor neuron weakness.
Similarly lateral extension results in Horner's syndrome, and dorsal extension causes
involvement of posterior column.
Selection of Candidates for Surgery
The likelihood of improvement of symptoms with surgery should influence the decision
to recommend surgery. All the clinical manifestations of syrinx associated with CM
type I do not respond equally to surgery. However, early diagnosis and surgical treatment
of syringomyelia are essential to arrest progressive myelopathy and prevent further
loss of neurologic function. Many authors[2] have recognized the prognostic value of certain clinical variables including clinical
syndromes. Suboccipital headache caused by tonsillar impaction respond well to adequate
decompressive therapy. Pyramidal tract manifestations and spinothalamic sensory loss
improve as pressure of the cysts on these pathways is reduced. Weakness and atrophy
of the hands show little improvement because of destruction of corresponding anterior
horn cells. Similarly dysesthetic pain that is a form of denervation dysesthesia due
to destruction of ascending spinal pathways with thalamic projection responds poorly
to decompressive therapy. Each patient must be judged individually keeping in mind
that progression of symptoms can sometimes occur rather abruptly. Because some of
the neurologic deficits tend to become fixed once developed, most patients with Chiari
and a distended syrinx must be candidates for surgery. CM presenting with lower cranial
nerve involvement or symptoms of direct brainstem compression must also be candidates
for surgery.[3]
Surgical Techniques Followed, Its Correlation to Underlying Pathophysiologic Mechanisms
and Recommendations
Improved understanding of the pathophysiology of syringomyelia encourages the design
and implementation of procedures directed toward eliminating the obstruction of CSF
pathways, that is, strategies designed to reverse the pathophysiologic process underlying
syringomyelia. The purpose of the operation is to enlarge the bony area of the craniocervical
junction and expand the dura, surrounding the brainstem to effectively open the CSF
pathways at the foramen magnum for providing effective and lasting treatment of syringomyelia
with low morbidity. The specific surgical steps in this operation continue to undergo
modification as surgeons attempt to identify the optimum treatment. This is usually
dictated by patient characteristics and surgeons experience.
The management strategy follows a “top down” rule.[4] Treatment always begins by addressing hydrocephalus, if it is present. A ventriculoperitoneal
shunt placed in patients with hydrocephalus may relieve both cerebellar ectopia and
dilatation of the central canal as well. In 1950, Gardner and Goodall at the Cleveland
Clinic recognized the association of the CM type I with syringomyelia.[5] They postulated that the outlets of the fourth ventricle were occluded by the CM
type I and that a water-hammer pulsation was directed from the fourth ventricle, through
the obex and into the central canal of spinal cord, leading to pulsatile expansion
of the central canal to form the syrinx. To reverse this process, Gardner performed
the surgical procedure that removed the bone from the posterior aspect of the foramen
magnum, opened the fourth ventricle to the subarachnoid space, and plugged the obex.[5] In the 1970 Logue introduced a less invasive alternative to Gardner's procedure.[6] His procedure consisted of simple bony decompression and expansion of the dura with
tissue graft and avoidance of opening of the arachnoid membrane and entrance into
the subarachnoid space or fourth ventricle. His group performed a clinical study comparing
Gardner's procedure with their procedure of simple decompression and duraplasty and
demonstrated that there was no difference in syrinx resolution between the procedures,
although the Gardner's operation resulted in higher complication rate.[6] Therefore, simple and least invasive craniocervical decompression and duraplasty
without opening arachnoid membrane that eliminates the pathophysiologic mechanisms
of syringomyelia was preferred in most of the cases in the later phase of our study.
A wide triangular pericranial graft harvested from the occipital region at the beginning
of procedure was our standard institutional practice. The foramen magnum and arch
of axis was exposed in the entire width of the dura, and more lateral exposure was
avoided due to risk of vascular injury. It was our institutional preference to preserve
muscle attachments and lamina of C2 intact to minimize postoperative pain and instability
with the exception of 11 cases in which tonsillar descent was below C2. There is controversy
regarding the extent of decompression required to alleviate symptoms. The importance
to find answer to question “how much is enough” in our study is magnified in patients
with CM type I because a significant proportion of these patients have small posterior
fossa volume. Data analysis in the initial phase of this study revealed greater belief
in wider foramen magnum decompression even up to extent of partial resection of medial
margins of occipital condyles. The distance between the midpoints of the condyles
is approximately 4.5 cm.[7] Resection of occipital condyles results in overt instability. In experimental studies
when 50% of a condyle was resected, the range of motion was found to be increased
by 153% during flexion extension, by 40.8% during lateral bending, and by 28.1% during
axial rotation. Condylectomy was also associated with an increase in rotation at C1–C2,
although not significantly when less than 75% of the condyle was resected.[8] Apart from craniovertebral instability, oversize craniectomy can result in cerebellar
ptosis due to herniation of tonsils and vermis with resultant adherence to overlying
graft leading again to obstruction of CSF flow and reappearance of syringomyelia.
Samii and Klekamp[9] have advised that the size of the craniectomy should be limited to the width of
the spinal canal and not to extend further upward than 2 cm from the rim of the foramen
magnum. There was no significant difference in outcome when more conservative approach
of limited removal of the bone to completely decompress the entire posterior surface
of the cerebellar tonsils was advocated. In this study, associated bony anomalies
were present in 20 (27%) patients in whom the occipital bone was considerably flattened
with rostral tilt at the foramen magnum and assimilation of the arch of atlas. In
patients with CM type I, the bones of the skull base often are underdeveloped in 25%
cases, resulting in skeletal anomalies such as basilar invagination (25–50%), Klippel-Feil
syndrome (5–10%), and atlanto-occipital assimilation (1–5%) that results in reduced
volume of posterior fossa.[10] In all of those patients, our institutional preference was to do preoperative CT
study of the craniocervical junction that was having important implications in operative
strategy for bony decompression. Grabb et al have described the entity of ventral
brainstem compression in pediatric and young adult patients with Chiari I malformations.[11] They have observed ventral cervicomedullary encroachment by the odontoid and its
investing tissues into the rostral spinal canal resulting in flattening and distortion
of the ventral brainstem in 28% of patients in their study. Significant ventral compression
was defined as greater than 9 mm of reclination of the odontoid process from a line
connecting the basion to the posterior aspect of the body of the axis. Their recommendation
for patients with measurements of 9 mm or greater, is the reduction in ventral brainstem
compression before posterior fossa decompression. In our subset of associated 25%
basilar invagination, all have less than 9 mm of reclination of the odontoid process
from a line connecting the basion to the posterior aspect of the body of the axis,
so we have done only posterior decompression for CM with syrinx associated with basilar
invagination.
Although conservative decompression was sufficient in most patients, few subsets of
patients having thick dural band and significant tonsillar descent required intradural
approach. Arachnoid adhesions are not directly visualized in conventional CT and MRI.
However, preoperative cinewave MRI, intraoperative visualization of movements of tonsils
seen through dura, and intraoperative ultrasound may help in deciding need for intradural
approach. The dura was opened in midline at the C1 level with incision extended superiorly
to split below foramen magnum to create Y-shaped dural opening. In all the cases in
which intradural exploration was done, endpoint was visualizing choroid plexus of
the fourth ventricle and free flow of CSF into subarachnoid space. In cases of severe
tonsillar ectopia, extrapial coagulation of tonsillar tip was preferable to facilitate
free flow of CSF from the foramen of Magendie. Capacious duraplasty using previously
harvested pericranial graft with reinforcement of suture line using fibrin glue to
prevent CSF leakage was our routine institutional practice. Older procedures of intervention
for syrinx without bony decompression done in earlier part of our study were discontinued
due to high recurrence rate and poor outcome. Overview of the literature about craniectomy
size, C1 arch removal, duraplasty, and tonsillar resection and arachnoid dissection
are listed in [Tables 6] to [9], respectively.[10]
[12]
[13]
[14]
[15]
[16]
[17]
[18]
[19]
[20]
Table 6
Literature overview related to craniectomy size in Chiari malformation type I
|
Author
|
No. of patients
|
Children/Adults
|
Extent of bone removal
|
|
Erdogan et al (2010)[10]
|
27
|
Both
|
Decompressive suboccipital craniectomy, at least 3 cm above foramen magnum, width
of 3 cm
|
|
Gurbuz et al (2015)[12]
|
39
|
Both
|
Decompressive suboccipital craniectomy, at least 3 cm above foramen magnum, width
of at least 4 cm
|
|
Kennedy et al (2015)[13]
|
156
|
Children
|
Suboccipital craniectomy
|
|
Kumar et al (2014)[14]
|
1
|
Adult
|
Suboccipital craniectomy
|
|
Mutchnick et al (2010)[15]
|
121
|
Both
|
Wide suboccipital craniectomy
|
|
Rehman et al (2015)[16]
|
21
|
Adult
|
Suboccipital craniectomy
|
|
Furtado et al (2011)[17]
|
20
|
Children
|
Midline suboccipital craniectomy, individualized according to age
|
|
Hoffman and Souweidane (2008)[18]
|
40
|
Both
|
Suboccipital decompression, superior extension of ~1.5–2 cm, lateral extension to
the lateral most aspect of the foramen magnum and cervical spinal canal
|
Table 7
Literature overview related to C1 arch removal in Chiari malformation type I
|
Author
|
No. of patients
|
Children/Adults
|
C1 arch removal
|
|
Erdogan et al (2010)[10]
|
27
|
Both
|
Total C1 laminectomy (removal of the atlantooccipital ligament and dural scarring
or bands on the dura outside)
|
|
Gurbuz et al (2015)[12]
|
39
|
Both
|
Total C1 laminectomy
|
|
Kennedy et al (2015)[13]
|
156
|
Children
|
Total C1 laminectomy and incision of the atlantooccipital ligament in all cases; additional
C2 partial laminectomy in 12 cases
|
|
Kumar et al (2014)[14]
|
1
|
Adult
|
C1 laminectomy (3 cm wide)
|
|
Mutchnick et al (2010)[15]
|
121
|
Both
|
Total C1 laminectomy and careful resection of dural bands
|
|
Rehman et al (2015)[16]
|
21
|
Adult
|
C1 laminectomy in all cases, additional C2 laminectomy in 2 cases
|
|
Furtado et al (2011)[17]
|
20
|
Children
|
C1 laminectomy in all cases, additional C2 laminectomy in 1 case
|
|
Hoffman and Souweidane (2008)[18]
|
40
|
Both
|
Extent of cervical laminectomy determined by degree of tonsillar descent
|
Table 8
Literature overview related to duraplasty in Chiari malformation type I
|
Author
|
No. of patients
|
Children/Adults
|
Materials
|
Results
|
|
Abbreviations: CSF, cerebrospinal fluid; FMD, foramen magnum decompression; MRI, magnetic
resonance imaging; n.m., not mentioned; PFD, posterior fossa decompression.
|
|
Abla et al (2010)[19]
|
Review of literature
|
Both
|
Autologous and nonautologous
|
Duraplasty essential because of creating a cisterna magna where one was not previously
present; no superiority of neither autologous nor nonautologous graft; pericranium
is preferred if possible
|
|
Erdogan et al (2010)[10]
|
n = 27 (15 FMD with duraplasty, 12 only FMD)
|
Both
|
Y–shaped opening and dural grafting with cadaveric dura
|
No statistical postoperative differences a dura opening recommended in cases of any
suspicion about maintaining CSF flow in the posterior fossa
|
|
Gurbuz et al (2015)[12]
|
n = 39 (21 duraplasty, 18 nonduraplasty)
|
Both
|
n.m.
|
No statistically significant difference for surgical results, but in regression of
postoperative syrinx size a in patients with syrinx, tonsillar herniation > 10 mm,
and symptom duration < 36 mo, duraplasty considered to be a more reliable choice despite
a slightly higher rate of complications
|
|
Hoffman and Souweidane (2008)[18]
|
n = 40
|
Both
|
Autologous pericranial tissue
|
PFD with duraplasty is safe and appropriate
|
|
Kennedy et al (2015)[13]
|
n = 156 (nonduraplasty)
|
Children
|
n.m.
|
Dura opening recommended for patients with rapid progression of neurologic deficits,
scoliosis with syrinx, craniovertebral instability requiring fusion, and if preoperative
MRI suggests that partial C2 laminectomy will be necessary
|
|
Mutchnick et al (2010)[15]
|
n = 121 (56 nonduraplasty, 64 duraplasty)
|
Both
|
Y–shaped incision extending caudal past the foramen magnum with a generous pericranial
patch, covered with Tisseel
|
Clear benefits to most children without duraplasty, but recurrence is slightly higher
than with duraplasty
|
|
Rehman et al (2015)[16]
|
n = 21
|
Adults
|
n.n.
|
PFD with duraplasty best treatment option
|
|
Furtado et al (2011)[17]
|
n = 20
|
Children
|
With pericranium or artificial dura
|
PDF with duraplasty preferred
|
Table 9
Literature overview related to tonsillar resection and arachnoid dissection in Chiari
malformation type I
|
Author
|
No. of patients
|
Children/Adults
|
Intervention done
|
|
Abbreviations: CSF, cerebrospinal fluid; PFD, posterior fossa decompression.
|
|
Erdogan et al (2010)[10]
|
27
|
Both
|
Opening of thick arachnoid layers and resection of thick arachnoid bands between the
tonsils can be necessary to obtain CSF passage
|
|
Furtado et al (2011)[17]
|
20
|
Children
|
Dense subarachnoid bands were released, and tonsils were shrunk with bipolar cautery
until free egress of CSF was seen from the foramen of Magendie
|
|
Guyotat et al (1998)[20]
|
75
|
Both
|
Better outcome in patients treated by PFD and additional tonsil resection
|
Conclusion
Chiari malformation type I presents a difficult challenge to neurosurgeons due to
its unpredictable clinical course and controversies regarding management. Our understanding
of managing this entity is still evolving, but innovative surgical techniques for
breaking barriers of CSF flow to restore normal CSF dynamics across the craniocervical
junction provide the pragmatic solution. The trend is toward balance between maximum
decompression and preserving normal integrity.
Informed Consent
Informed consent was obtained from all individual participants included in this study.
Declaration of Patient Consent
The authors certify that they have obtained all appropriate patient consent forms.
In the form, the patients have given their consent for their images and other clinical
information to be reported in the journal. The patients understand that their names
or initials will not be published and due effort will be made to conceal their identity,
but anonymity cannot be guaranteed.
Financial Support and Sponsorship
None.
