Coexistent Chiari Malformation JSM Neurosurgery and Spine Central

JSM Neurosurgery and Spine
Central
Case Report
Coexistent Chiari Malformation
and Idiopathic Intracranial
Hypertension: Which Should Be
Treated First?- Case Report and
Review
Michael S. Park1*, Puya Alikhani1 and Gerald F Tuite2
1
2
Department of Neurosurgery & Brain Repair, University of South Florida, USA
Neuroscience Institute, All Children’s Hospital / Johns Hopkins Medicine, USA
Abstract
*Corresponding author
Michael S Park, Department of Neurosurgery & Brain
Repair, Morsani College of Medicine, University of
South Florida, 2 Tampa General Circle, 7th Floor,
Tampa, FL 33606; USA, Tel: 18132590901; Fax:
18132590944; Email:
Submitted: 05 February 2014
Accepted: 03 March 2014
Published: 20 March 2014
Copyright
© 2014 Park et al.
OPEN ACCESS
Keywords
•Chiari Malformation (CM
•Type I, CM1)
•Idiopathic Intracranial Hypertension (IIH)
•Pseudotumor Cerebri
•Foramen Magnum Decompression and Duraplasty
(FMDD)
Previous reports have described concomitant presentation of papilledema
and Chiari malformation type 1 (CM1). The pathophysiology of each and their
relationship remain poorly understood. As such, different management approaches
regarding treating the CM1 or the pseudotumor initially have been described, with
varying degrees of success. We report the case of an 11 year old girl with 6 mm
tonsillar herniation, a cervicothoracic syrinx, and papilledema who underwent foramen
magnum decompression with duraplasty (FMDD). Intracranial pressure (ICP) monitoring
revealed elevated ICP before surgery, which resolved postoperatively. The patient had
complete resolution of all symptoms and her papilledema and syrinx also resolved.
ABBREVIATIONS
CASE PRESENTATION
CM: Chiari Malformation; CM1: Chiari Malformation Type
I; IIH: Idiopathic Intracranial Hypertension; ICP: Intracranial
Pressure; FMDD: Foramen Magnum Decompression and
Duraplasty; MRI: Magnetic Resonance Imaging; CT: Computed
Tomography; LP: Lumbar Puncture
This 11-year-old girl was diagnosed with migraine headaches
at age 5, which resolved after 6 months of prophylactic headache
medication. Frontal headaches returned 6 years later and became
associated with intermittent blurry vision and photophobia but
not emesis; they were not exacerbated by coughing, sneezing, or
physical exertion. She was born at term with no other medical or
family history.
INTRODUCTION
Previous reports have presented cases of concomitant
Chiari malformation type 1 (CM1) and Idiopathic Intracranial
Hypertension (IIH) [1-19]. These are two common but
incompletely understood diagnoses with similar clinical
presentations; [1-4,6] a pathophysiologic relationship between
the two related to craniocephalic disproportion has been
suggested [3]. In this setting, knowing which to treat first can
be difficult. Some suggest treating IIH first, [1,10,13] while
others have described treating IIH after failed foramen magnum
decompression with duraplasty (FMDD) [3,6,7,20]. We present
a patient with Chiari I malformation, syringomyelia and
bilateral papilledema successfully treated with FMDD alone,
raising provocative questions about common etiologies and the
possibility that there are more undiagnosed cases of coexistent
IIH and CM1 that may respond well to FMDD rather than medical
treatment.
Physical examination showed a healthy and neurologically
intact 38 kg female except for the presence of bilateral
papilledema, which was not present at age five. MRI of the
brain (Figure 1) and spine (Figure 2) showed 6 mm of tonsillar
displacement at the foramen magnum, syringomyelia between
C5 and T9 (4.5 mm in maximal diameter), and no evidence of
tethered spinal cord or low-lying conus. CT and MR venography
of the head and neck were negative.
Continuous intracranial pressure (ICP) monitoring (Camino
Intracranial Pressure Monitor, Integra Life Sciences Corp) for 24
hours prior to FMDD showed fluctuating but consistently elevated
ICP between 25 and 40 mm Hg, when relaxed. Foramen magnum
decompression, C1 laminectomy, dural opening, shrinking of
the cerebellar tonsils, and expansile duraplasty with autologous
pericranium was performed under a separate anesthetic. No
Cite this article: Park MS, Alikhani P, Tuite GF (2014) Coexistent Chiari Malformation and Idiopathic Intracranial Hypertension: Which Should Be Treated
First?- Case Report and Review. JSM Neurosurg Spine 2(3): 1025.
Park et al. (2014)
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veil of tissue, as described by Tubbs [21] was appreciated as the
cerebellar tonsils were separated.
The Camino monitor was left in place after Chiari
decompression, confirming ICP normalization to the 5-15 mm
Hg range. Her postoperative course was uneventful. She had
complete resolution of her symptoms and papilledema on
dilated fundoscopic examination at her 6 week office visit. Her
postoperative MRIs are shown in Figure 3 and Figure 4. At 9
months’ follow up, papilledema remained absent and the syrinx
was nearly resolved.
DISCUSSION
The relationship between IIH and CM has been established
but is poorly understood, with some clinical overlap between
the two. There is a predilection for females of child bearing
age in both disorders [22,23]. Obesity is strongly associated
with IIH, but this has not been described for CM1. Presenting
symptoms of both CM1 and IIH include headaches, paresthesias,
visual disturbances, visual loss, shoulder/arm pain, diplopia,
motor weakness, and numbness, and these symptoms may be
exacerbated by Valsalva maneuver in both cases [3]. Bilateral
papilledema is the hallmark of IIH but has also been reported in
CM1 [4,11,12,15-17,19,24].
Radiographs are not absolutely diagnostic for either entity.
Although CM1 is defined by herniation of the cerebellar tonsils
below the foramen magnum of 5 mm or more, [12] not all
patients with this finding are symptomatic or require surgical
intervention [25,26]. Conversely, there are patients not meeting
radiographic criteria for CM1 who are symptomatic. Aiken and
Barkovic have reported a mean tonsillar location in control
patients between 0.7 to 1 mm above the foramen magnum with a
standard deviation of 1.9 mm; based on this, a small percentage
of control patients would be expected to have a tonsillar location
of 2.8 to 3.1 mm below the foramen magnum. The correlation
between the degree of tonsillar herniation and presence and
severity of symptoms is imperfect.
Figure 2 MRI Cervical spine, T1 weighted image, midsagittal view,
demonstrating cervicothoracic syrinx.
Figure 3 Postoperative MRI Brain, T1 weighted image, midsagittal view.
For IIH, radiographic evaluation is less helpful. Absence of a
mass lesion or other cause of increased ICP is required for the
diagnosis of IIH as part of the modified Dandy criteria [23,27].
However, findings of optic nerve sheath enlargement and
tortuosity, empty sella syndrome, reversal of the optic nerve
head, transverse sinus stenosis, and flattening of the posterior
sclera have been reported [8,28]. Tonsillar herniation has been
reported to have a higher incidence in patients with IIH, ranging
from 1.3% to 5.9%, compared to an incidence of 0.77% in the
general population without CM1; [1-3,9] one author reported an
eight-fold increase in CM1 in IIH patients [3].
Figure 1 MRI Brain, T1 weighted image, midsaggital view, demonstrating 6
mm of tonsillar herniation.
JSM Neurosurg Spine 2(3): 1025 (2014)
Additional uncertainty regarding the management of
concurrent CM1 and IIH stems from an incomplete understanding
of the pathophysiology of each disorder and any relation
between the two; it is unclear if CM causes IIH or if raised ICP
from IIH causes tonsillar displacement. One argument is that
tonsillar herniation causes alterations in CSF flow dynamics at
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pathophysiology of both disorders, and its chicken-andegg nature, it is unclear if the primary treatment should be
acetazolamide (for IIH) or FMDD (for CM1). To our knowledge,
there is only one case of successful primary acetazolamide
treatment for concomitant CM1 and IIH leading to resolution
of tonsillar herniation [17]. Other reports in which the IIH was
treated first have yielded satisfactory results with regards to the
IIH, but without change in the CM; [1,10,13] one author concluded
that the two entities were coincidental [31]. Additional reports
have described development or exacerbation of CM1 following
treatment for IIH, requiring subsequent treatment with FMDD
[1,4,5,16].
Figure 4 Postoperative MRI Cervical spine, T1 weighted image, demonstrating
resolution of syrinx.
the foramen magnum. This could occur by a partial ball-valve
mechanism, [29] with reduced dampening effects to pressure
changes and altered CSF-brain compliance [22]. Abnormal
torcula position and compression of draining veins, [16,30] as
well as arachnoid scarring from rubbing of the tonsils against
bone have also been hypothesized as causative factors [31,32].
Ultimately there is CSF obstruction at the foramen magnum [33]
with creation of a CSF pressure gradient between the cranial and
cervical compartments [29,34]. The demonstration of 4-8 mL CSF
flow across the foramen magnum during periods of Valsalva, with
0.6 mL CSF flow caudally with transmission of resting cardiac
impulse, [35] combined with a ball-valve mechanism allowing
ingress of CSF into the cranial compartment without allowing
sufficient egress into the cervical compartment would lead to
increased ICP and IIH.
Acquired inferior tonsillar displacement has been reported,
usually following lumbar CSF diversion [9,14,33,36,37]. Tonsillar
herniation has also been reported in association with both
supra- and infratentorial mass lesions and hydrocephalus, with
resolution of the tonsillar herniation after primary treatment of
the cyst, tumor or hydrocephalus [38-40].
Bejjani
hypothesizes
that
relative
craniocephalic
disproportion could account for both; a small posterior fossa could
give the tonsillar herniation associated with CM1 and compound
the effects of brain engorgement from venous stasis or altered
CSF absorption [3]. This idea of craniocephalic disproportion,
as well as the association of CM1 with achondroplasia as well as
osteochondrodysplastic and craniofacial disorders (e.g., Apert,
Crouzon), is consistent with Milhorat’s theory of CM1 being a
disorder of mesenchymal origin [9,12,22]. At the same time, the
notion of impaired CSF absorption due to constriction of cerebral
venous drainage and/or a dynamic effect both exerted on and by
the superior sagittal sinus leading to increased brain turgor has
also been postulated as a cause of both slit-ventricle syndrome
and so-called normal volume hydrocephalus [30].
Given the current level of understanding regarding the
JSM Neurosurg Spine 2(3): 1025 (2014)
Other cases of concomitant CM1 and IIH describe primary CM1
treatment with resolution of papilledema, besides this case report
[11,16,18,19]. In two of these, ICPs were elevated preoperatively
and normal postoperatively [11,18]. In another, FMDD effected
resolution of papilledema, but the patient developed optic nerve
atrophy and residual visual field deficit [19].
Fagan described a “Chiari Pseudotumor Cerebri Syndrome”
in which patients developed recurrent Chiari-like symptoms,
elevated opening pressure on LP, and transient relief with high
volume CSF drainage following FMDD, ultimately proceeding to
shunting. They postulated that FMDD altered CSF compliance at
the foramen magnum, providing temporary relief, but that the
underlying IIH remained until CSF diversion, [6] a theory also
espoused by Bejjani. In his series of 6 patients of FMDD for CM1,
however, none had papilledema; as the dura became fibrotic
following surgery, the compliance was altered further, and all
six proceeded to CSF diversion. He postulated that they had IIH
without papilledema preoperatively [3]. Additional treatment
failures with FMDD have been described, requiring subsequent
pharmacologic treatment in one case [7] and ventriculoperitoneal
shunting after elevated ICPs 2 years postoperatively were found
in another [20].
We present a case of coexistent papilledema, CM1 and syrinx
successfully treated with FMDD, raising the possibility that
FMDD should be considered more frequently as the treatment of
choice for concomitant papilledema and CM1, particularly when
syrinx is present. Unfortunately, in our review, only in one case
was spinal cord syrinxes present [10].
In the absence of a syrinx, the evaluation and clinical
judgment are critical. Workup and treatment of hydrocephalus
is the first priority, but if negative, the presence of papilledema,
together with the data likely accrued to this point in the workup
(i.e., referable signs and/or symptoms, tonsillar herniation,
papilledema, and absence of hydrocephalus) leads to several
options, including ICP monitoring, acetazolamide trial, and
FMDD, and raising the fundamental question raised by this case.
Additional findings such as spinal cord syrinx, scoliosis, or bulbar
signs and symptoms may favor FMDD over the others [10].
Proceeding with FMDD, as in this case, would address the CM1
and the papilledema (or IIH) can be followed postoperatively.
The management would revert to that as for IIH without tonsillar
herniation, including LP, acetazolamide, optic nerve sheath
fenestration, and shunting, although FMDD may decrease ICP
through several mechanisms, as discussed earlier, [3,6] and
obviate the need for CSF diversion. Although it has been argued
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that FMDD in the setting of elevated ICP leads to an increased risk
of CSF leak, [10] we believe this risk to be small.
CONCLUSION
In this case, we proceeded directly with FMDD; this was
largely driven by the presence of the cervicothoracic syrinx. It
would also be reasonable to proceed with FMDD in the presence
of neurological deficits, especially bulbar signs. As the preceding
discussion illustrates, the management of concomitant Chiari
I malformation and papilledema can be complex. This case and
review of the literature are presented in the hope that it may
guide management of similarly challenging cases.
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Cite this article
Park MS, Alikhani P, Tuite GF (2014) Coexistent Chiari Malformation and Idiopathic Intracranial Hypertension: Which Should Be Treated First?- Case Report and
Review. JSM Neurosurg Spine 2(3): 1025.
JSM Neurosurg Spine 2(3): 1025 (2014)
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