Key-words:
Arachnoid cyst - intramedullary - spinal cord
Introduction
Intramedullary spinal cord tumors represent about 5% of all spinal cord tumors.[[1]] The most common types described are astrocytoma and ependymoma. Arachnoid cyst
represents a rare entity, especially in the thoracic area. They are mostly extradural
and asymptomatic, though sometimes can be intradural extramedullary. Pediatric age
groups develop arachnoid cyst more frequently either congenital, posttraumatic, postinfectious,
secondary to kyphoscoliosis, or spinal dysraphism.[[1]] Based on our literature review, only nine cases were reported in the pediatric
age groups [[2]],[[3]],[[4]],[[5]],[[6]],[[7]],[[8]],[[9]] and eight cases in the adult age groups.[[5]],[[10]],[[11]],[[12]],[[13]],[[14]],[[15]],[[16]] Here, we present an interesting case of thoracic intramedullary spinal tumor in
an adult patient presenting with myelopathic symptoms and signs with marked regression
of the cyst and remarkable clinical improvement early postoperatively and during follow-up.
History of Presenting Illness
A 31-year-old male presented to our clinic complaining of heaviness and vague sensation
in his lower limbs and lower part of his trunk, slowly progressive over 2-year duration.
Three months before his presentation, he experienced back pain and difficulties in
passing urine (weak stream) and constipation which was progressing. On further questioning,
the patient also mentioned recent history of impotence and frequent falls while walking.
Clinical examination
The clinical examination showed he was fully awake; moving all his limbs; mild spasticity
in both the lower limbs; unstable gait; sensory level in the form of bilateral hypoesthesia
from D6 down below; motor power in both the lower limbs was 4/5 in all muscle groups,
with well-sustained bilateral clonus; exaggerated deep jerk reflexes all over the
lower limbs; and intact anal tone.
Imaging
Whole spine X-ray showed mild thoracic and mild thoracolumbar scoliosis with convexity
toward the left at the midthoracic region (mild thoracic levoscoliosis) and to the
right at the upper lumbar region (mild lumbar dextroscoliosis) [[Figure 1]].
Figure 1: Whole spine X-ray showing mild thoracic and mild thoracolumbar scoliosis with convexity
toward the left at the midthoracic region (mild thoracic levoscoliosis) and to the
right at the upper lumbar region (mild lumbar dextroscoliosis)
Magnetic resonance imaging spine showed midthoracic intramedullary cystic lesion (2.5
cm), extending along T6, T7, and T8 level with 9.5 mm width. Of note, secondary developed
syrinx at the lower part of the lesion corresponding to T8–T9 level. The lesion was
hypointense on T1 and hyperintense on T2-weighted sequence. Postcontrast sequence
showed no enhancement [[Figure 2]].
Figure 2: (a) Magnetic resonance imaging T1 and T2 sagittal. (b) Magnetic resonance imaging
T2 axial and T2 Sagittal. (c) T1 sagittal pre- and postcontrast gadolinium-based enhancement
Hospital course
Urodynamic testing was done on outpatient department basis, showing obstructive void
pattern with normal detrusor pressure, which could be related to the spinal lesion.
The patient was then electively admitted for surgery.
Operation
-
The patient underwent D6–D8 laminectomy
-
The dura was then opened longitudinally in the midline. Abnormally thickened arachnoid
was encountered which was carefully dissected
-
Abnormal-looking area was noted at the upper part of the dural opening; after arachnoidal
adhesions were divided, the cord was spotted to be extremely swollen and protruding
out
-
An abnormal grayish area was seen on the right side of the cord which was also adherent
to arachnoid
-
Multiple biopsies of this lesion were done
-
This was not separable from the cord and medially there was no clear boundary between
the lesion and the cord; hence, it was not attempted for complete excision
-
After taking biopsy, midline myelotomy for about 1 cm was carried out distal to lesion
by a sharp knife followed by micro dissector and fine forceps dissection down the
midline
-
A larger syrinx was entered and was decompressed
-
Soon after the cord appeared to be lax and pulsating
-
Hemostasis was secured, and the dura was closed using running stitches
-
Valsalva was done to confirm no cerebrospinal fluid leakage
-
DuraGen was applied and then tissel was overlaid the dura. Wound was closed in layers
in standard fashion.
Surgical pathology
Arachnoid cyst [[Figure 4]].
Postoperative course
In postoperative period during his stay in the hospital, there was clinical improvement
in his gait and motor power.
The Patient was then transferred to the rehabilitation unit for intensive rehabilitation,
and he was able to ambulate independently and to control his bowel/bladder with subtle
residual spasticity. Sensation was same as preoperative status, which improved after
few weeks.
MRI about 3 months postoperative showed postoperative changes with regression of intramedullary
cystic lesion [[Figure 3]].
Figure 3: (a) Magnetic resonance imaging T1 and T2 sagittal postoperative. (b) T2 axial and
sagittal postoperative. (c) T1 sagittal pre- and postcontrast gadolinium-based postoperative
Figure 4: Microscopic view showing a thickened cyst wall containing numerous psammomatous calcifications
and has flat lining (H and E, x200). Pathological examination of the tissue revealed
a cyst with thickened fibrous wall that contains numerous psammomatous calcifications
and has flat denuded lining. Immunohistochemistry was performed and showed the flat
lining to be positive with EMA while negative with S100, GFAP, and cytokeratin cocktail
Follow-up
The patient was seen in the clinic 50 days after discharge from the hospital and he
reported dramatic improvement in the radicular pain, erectile dysfunction, and lower
limb weakness.
Discussion
Arachnoid cyst is a rare presentation of spinal cord tumors. Even when found, they
are mostly extradural or intradural extramedullary. Extradural cysts usually originate
from arachnoid herniation, but intradural cysts originate from arachnoid trabeculations.
Intramedullary arachnoid cysts are very rare and their origin, risk factors still
not well understood.[[14]] Most of the cases reported in the literature are mainly pediatric with some reported
cases in adults. Hence, this may explain the relations of intramedullary arachnoid
cyst to genetic factors or developmental anomalies. A case reported discussing the
association of intramedullary arachnoid cyst with cervical myelopathy which may play
a role in its pathogenesis.[[15]] Although most arachnoid cysts are asymptomatic, our case presented with myelopathic
symptoms which improved postoperatively.
Some research studies appeared recently investigating the surgical outcome of arachnoid
cyst and showed that their results are promising. Most patients show marked improvement
which may change the surgeon's decision to operate on spinal arachnoid cysts even
if asymptomatic to decrease risk of myelopathy.[[17]]
Conclusion
We recommend surgery for symptomatic arachnoid cysts and those asymptomatic cysts
that appear to have progressive overt clinical impairment on follow-up. We should
discuss with our patients the future risk of myelopathy and the need for surgery at
any point once the asymptomatic cyst started to have neurological impairment. Furthermore,
more research is needed to address the risk factors associated with this type of cysts
and less invasive surgical techniques to be developed.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms.
In the form the patient(s) has/have given his/her/their consent for his/her/their
images and other clinical information to be reported in the journal. The patients
understand that their names and initials will not be published and due efforts will
be made to conceal their identity, but anonymity cannot be guaranteed.
