Keywords
cervical - arachnoid cysts - trans-disc
Introduction
Spinal arachnoid cysts are rare entities occurring mainly in the thoracic or cervical
spine.[1] Their etiology is linked to defects in the dura mater that may be congenital, traumatic,
or iatrogenic. As a result, the arachnoid may protrude through these defects, thereby
resulting in cyst formation.[1]
[2] Neurenteric cysts however are rare lesions that arise due to inappropriate partitioning
of the embryonic notochord plate and presumptive endoderm during the third week of
development.[1] Often, these cysts may cause compression of the spinal cord resulting in clinical
features of myelopathy.[2]
[3]
A review of the literature suggests that the majority of authors treat these lesions
by posterior laminectomy or laminotomy.[4]
[5]
[6]
[7]
[8] Associated complications with this approach include progressive kyphotic deformities,
especially in children.[9] Some authors aim to minimize this by performing laminoplasties yet extensive soft-tissue
dissection is still required. A few reports utilize decompression by anterior approaches
via corpectomy as the long-term effect on mobility generally is significant considering
a potential multilevel fusion. In addition, the technical challenges and risks of
anterior cervical intradural work have to be considered. We describe a series of four
procedures, whereby trans-disc and trans-vertebral aspiration of arachnoid cysts have
been performed in the cervical spine.[8]
[9]
[10]
[11]
[12]
Operative Technique
A standard Smith–Robinson approach was utilized to expose the appropriate level, supported
by fluoroscopy. Once the level was identified and adequately exposed, a 22-gauge spinal
needle with its stylet is passed through the disc ([Fig. 1]) supported by continuous fluoroscopy. If the cyst is best accessed through the vertebral
body as opposed to the disc, a small 3 mm channel is drilled up to the posterior longitudinal
ligament in the midline. The spinal needle is then passed to drain the cyst. The cervical
canal can accurately be measured preoperatively and correlated with fluoroscopy measurements
making accurate needle (and specifically the bevel of the needle) placement possible.
The bevel must be passed completely into the cyst at least 1 mm past the posterior
vertebral body line or posterior margin of the disc. When the placement of the needle
is confirmed, the stylet is removed and the cyst aspirated. Volume calculation of
the cyst preoperatively guides the total volume aspirated safely.
Fig. 1Lateral X-ray of cervical spine showing position of spinal needle and saggital T2
MRI of anterior cervical arachnoid cyst with mass effect on spinal cord.
Case Series
Case 1
A 23-year-old man, a builder by profession, presented with an extended history and
clinical features suggestive of cervical myelopathy, rendering him bed-bound. Progressive
deterioration included loss of fine motor function, difficulty ambulating, and urinary
incontinence.
A magnetic resonance imaging (MRI) scan demonstrated a large anterior cervical cyst
dorsal to the C4 and C5 vertebral bodies ([Fig. 2]).
Fig. 2 T2-weighted image demonstrating an anterior cervical cyst.
He was managed in an outreach facility with limited equipment. This prompted the senior
author and his orthopedic colleague to attempt this procedure.
A trans-disc aspiration was performed as described in the operative technique above.
Postoperatively, the patient's symptoms resolved and he returned to his occupation
unhindered. When reviewed at the 6-month outpatient clinic follow-up, he was noted
to be asymptomatic with an unremarkable neurological examination. Repeat MRI showed
a significantly smaller cyst remnant with a cerebrospinal fluid (CSF) flow void suggesting
containment of the residual cyst ([Fig. 3]).
Fig. 3 Postoperative T2-weighted image demonstrating collapse of the cyst.
The patient remained asymptomatic at subsequent outpatient clinic follow-up appointments.
Case 2
A 6-year-old boy presented to the deformity clinic with a 3-month history of progressive
difficulty to walk and at the time of presentation had an opisthotonic posture and
was unable to ambulate.
With the exception of abnormal posture, his examination findings revealed a normal
motor and sensory examination.
Plain film X-rays demonstrated an exaggerated lumbar lordosis but no scoliosis or
bony defects ([Fig. 4]).
Fig. 4 X-ray demonstrating opisthotonus.
MRI revealed a 15 × 10 × 16 mm cystic lesion with CSF signal characteristics and a
thin hypointense rim on T2-weighted imaging, situated just inferior to the craniocervical
junction (C1–C3). Significant pressure on the spinal cord was demonstrated with posterior
compression ([Fig. 5]).
Fig. 5 Arachnoid cyst pre-aspiration, the second cyst demonstrated after initial cyst aspirated,
follow-up at 3 months.
The patient subsequently came forward for trans-disc aspiration of this cyst as per
the operative technique described above.
The patient's symptoms improved dramatically in the immediate postoperative period.
His gait returned to normal and his opisthotonus resolved. He was discharged home
on the third postoperative day, able to run already.
Nine months later, the patient re-presented with acute onset neck and back pain and
opisthotonus. Once again, his clinical examination was unremarkable. He was symptom-free
since the previous procedure.
An urgent MRI scan demonstrated no evidence of recurrence of the previously documented
arachnoid cyst, but a new cystic lesion was noted from the C7 level to the T3 level
with a mass effect on the spinal cord. No myelopathic changes were appreciated on
this imaging ([Fig. 5]).
A trans-disc aspiration was performed at the level in question (C7/T1). The procedure
was uneventful and the patient regained complete function immediately postoperatively.
A 3-month follow-up MRI scan revealed complete decompression of the spinal cord with
no evidence of the arachnoid cysts ([Fig. 5]). In hindsight, the second cyst can be appreciated in the first MRI yet was overshadowed
by the large upper cervical cyst. There was no evidence of any changes to the intervertebral
discs through which the needle was passed.
Case 3
A 57-year-old male patient presented to our department with a 2-month history of neck
pain and progressive quadriparesis. Examination revealed globally brisk reflexes,
increased bilateral limb tone, 2/5 power in all limbs, and a sensory level at C3.
MRI findings were consistent with an anterior cervical arachnoid cyst and spinal cord
compression at the C2 level.
The patient came forward for a transoral trans-dens cyst aspiration.
The level was confirmed fluoroscopically and a 3 mm burr was used to create midline
trans-oral access to the posterior cortex. A spinal needle was then used to enter
the cyst and the contents aspirated.
The patient initially improved to power 4/5 in all limbs, but within 5 days returned
to pre-surgical levels. A repeat MRI showed recurrence of the cyst, yet access to
it was demonstrated. A repeat aspiration was performed and a similar postoperative
course of initial improvement followed by deterioration back to the baseline was again
observed. This led to an open posterior procedure with cyst excision and subsequent
clinical resolution of symptoms. At 3 months, the myelopathy resolved and a follow-up
MRI demonstrated no cyst recurrence.
Histological analysis confirmed an arachnoid cyst.
Discussion
There are only 24 previously reported cases of anterior cervical arachnoid cysts in
the English literature.[13]
[14] Our series contributes an additional four to the existing body of knowledge but
describes a novel method in the management thereof, which can be considered minimally
invasive.
Surgical approaches to these cysts usually involve a laminectomy or laminoplasty with
access to the cyst from a dorsolateral trajectory. Anterior cervical corpectomy is
the alternative if posterior approaches cannot be used. These procedures are invasive
and have associated morbidity. These include hemorrhage, possible CSF leaks due to
challenging dural closures, and multilevel fusions after corpectomy with its associated
restricted motion and complications over time.[15] It would be preferential to avoid these procedures when a safe alternative is available.
Posterior approaches involving laminectomy or laminoplasty are associated with postoperative
pain, wound sepsis risks, and potential kyphotic deformity over time.[16] Risk to neural structures is equally important in both approaches.
Three of the four procedures resulted in complete clinical resolution at the 6-month
follow-up with excellent radiological results. No degeneration of the intervertebral
disc through which the needle was passed could be demonstrated on postoperative MRI
scans. One patient initially improved and then slowly deteriorated within the first
5 postoperative days. The conclusion was that it re-filled and a standard posterior
approach was utilized to excise the cyst after MRI confirmation with a good clinical
result. No morbidity was suffered from the anterior approach.
We believe this approach is minimally invasive and should it fail, pose no ill effect
to the patient nor the tissues involved with the benefit of potentially avoiding extensive
procedures. MRI scanning is advised at 6 months or earlier if clinical improvement
is not demonstrated.
