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ORIGINAL ARTICLE
Ahead of print publication
 

Extradural spinal arachnoid cysts: Management and outcome in five children


1 Department of Neurosurgery, Dr. Ram Manohar Lohia Institute of Medical Sciences (RMLIMS), Lucknow, Uttar Pradesh, India
2 Department of Radiodiagnosis and Imaging, Dr. Ram Manohar Lohia Institute of Medical Sciences (RMLIMS), Lucknow, Uttar Pradesh, India

Date of Submission19-May-2021
Date of Decision22-Oct-2021
Date of Acceptance19-Nov-2021
Date of Web Publication07-Jan-2022

Correspondence Address:
Deepak Kumar Singh,
Department of Neurosurgery, Dr. Ram Manohar Lohia Institute of Medical Sciences (RMLIMS), Lucknow, Uttar Pradesh.
India
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/jpn.JPN_113_21

 

   Abstract 

Background: Spinal extradural arachnoid cysts (SEACs) are rare lesions, which may become symptomatic due to mass effect or nerve root compression. They are discrete pockets of cerebrospinal fluid (CSF) communicating with subarachnoid space. These cysts may be single or multiple. Multiple cysts in the pediatric population are very rare, of which a few are reported to date. Materials and Methods: Here, we present a case series of five pediatric patients diagnosed with symptomatic SEACs and operated in our institute between the period of October 2017 and January 2021. The patients underwent surgery for excision of the cysts and closure of dural defects. The results were analyzed in terms of the clinical symptoms, location of cyst, surgical procedure performed, and outcome after surgery. Result: The mean age of presentation was 12 years. Common presenting complaints were lower limb weakness, pain, and bladder involvement. The median duration of symptoms before surgery was 7.8 months (mean 3 ± 12 months). Excision of cyst wall with closure of dural defect was done in all cases except one, in which the dural defect was not found. All cases gained near-normal muscle strength of lower extremities over a variable period of time after surgery. Conclusion: Pathogenesis of SEAC is not completely understood. Intraoperative localization and closure of the dural defect is the single most important step for excellent outcome.


Keywords: Arachnoid cysts, pediatric spine tumors, SEAC, spinal extradural arachnoid cysts, spinal tumors



How to cite this URL:
Singh DK, Nayak S, Singh N, Agrahari VK, Chhabra A. Extradural spinal arachnoid cysts: Management and outcome in five children. J Pediatr Neurosci [Epub ahead of print] [cited 2022 Jun 29]. Available from: https://www.pediatricneurosciences.com/preprintarticle.asp?id=335185





   Introduction Top


SEACs are a very rare entity, accounting for less than 1% of all primary spinal space-occupying lesions.[1],[2] These cysts are found in all age groups but most commonly in adolescents. Most commonly, they are found in the thoracic spine, followed by the lumbosacral and thoracolumbar regions.[2],[3],[4] They can produce a wide range of symptoms, from back pain to severe myelopathy, though they may be found as incidental lesions without symptoms.[5] They are believed to arise from congenital defects in the dura mater, and they almost always communicate with the intrathecal subarachnoid space through a small defect in the dura. The mainstay of treatment in patients with neurological symptoms is surgical removal of the cyst together with ligation of the communicating pedicle and closure of the dural defect.[2],[3],[5],[6]


   Materials and Methods Top


Here, we present case series of five pediatric patients diagnosed with symptomatic SEACs and operated in our institute between the period of October 2017 and January 2021 [Table 1]. The patients underwent surgery for excision of the cysts and closure of dural defects. The results were analyzed in terms of the clinical symptoms, location of cyst, surgical procedure performed, and outcome after surgery.
Table 1: Representative cases

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   Illustrative Cases Top


Case 1

A 14-year-old boy presented with a four-month history of progressive bilateral leg weakness that was causing gait clumsiness. He complained of an unusual pain sensation in his knees and legs bilaterally while walking.

He also experienced frequent stumbling and falls. The patient had a clumsy gait and bilateral leg weakness (spastic paraparesis was noted to extend from the sensory level of D-7 down with exaggerated lower limb reflexes).

Midsagittal and axial T1- and T2-weighted thoracic spine MR images demonstrated two cystic lesions causing spinal cord compression. The cord was flattened and displaced anteriorly extending from D-4 to D-8 [Figure 1]A and B. Axial T2-weighted images obtained at D 4 and D6 clearly showed that the cystic lesions were extradural in location [Figure 1]C and D. The cysts contained fluid that had the same signal characteristics as CSF on MR sequences. They compressed the thecal sac and spinal cord ventrally.
Figure 1: (Case 1) Mid-sagittal T2-weighted (A) and T1-weighted (B) thoracic spine MRI images showing two distinct extradural cystic lesions of CSF intensities. Characteristic extradural fat hyperintensities surrounding the lesions noted in TIW images. Axial T2-weighted (C) and T1-weighted (D) images delineating lateral extent of the lesion. Spinal cord is pushed anteriorly. Intraoperative images obtained after D4 to D8 laminotomy. (E) Two separate extradural cystic lesions identified (arrows)

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A D4-8 laminectomy was performed. Two separate extradural cysts were noted. One cyst extended from the lower border of D-4 to D-6, and the other extended from D-7 to D-8 [Figure 1E].The cysts were easily separated from the dura, which had been pushed forward by the cyst and appeared to arise from a small neck protruding through a defect in the dura of the left D-5 and right D-7 nerve root. Both of the cyst necks were excised, and the dural defect was sutured in a water-tight fashion. The spinal cord was completely decompressed.

The patient’s signs and symptoms improved, and by the time of hospital discharge, the strength in his lower extremities was up to normal. He was advised to wear a thoracic brace to prevent progressive kyphosis after the extensive laminectomy procedure. There was no radiological recurrence at 1-year follow-up, though Cobbs angle increased by 30

Case 2

A 9-year-old boy presented with a 1-year history of mid back pain and progressive spastic paraparesis with bladder bowel involvement that led to bedridden status. The patient also had a decreased sensation below D6. The MR images demonstrated extradural CSF intensity cystic lesions from D6 to L2 causing spinal cord compression [Figure 2]A–D.
Figure 2: (Case 2) (A and B) Mid-sagittal and axial T2 (A, C) and T1-weighted (B, D) thoracic spine MRI images showing three distinct extradural cystic lesions of CSF intensities. Axial images (C and D) showing compression of the cord anteriorly and thinning of posterior bony elements. Bony vertebral anomaly in mid-sagittal images warrants laminoplasty in this case. Intraoperative image after D5 to L2 lamina removal. (E) Three separate extradural lesions were identified

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The D5 to L2 lamina was exposed through a posterior midline incision. By using an ultrasonic bone cutter, D5 to L2 lamina was raised in a single piece for laminoplasty. Three separate cysts were noted: One extended from D6 to D9, the second from the lower border of D10 to the upper border of D11, and the third from the lower border of D11 to the lower border of L2. Cyst wall was excised, and dural defects were identified at left D6, D10, and D12 nerve roots [Figure 2E].

All dural defects were repaired in a watertight fashion with Silk 4-0 and covered with muscle, surgical fibrillary, and glue. A subarachnoid lumbar drain was also placed to prevent potential CSF leak. Laminas were replaced back and fixed using miniplates and screws.

The patient’s power improved significantly during the immediate postoperative period and at the time of discharge he was able to walk with the support of a crutch. At 1-year follow-up, he required minimal support and was on self-intermittent catheterization for bladder symptoms. The patient was wearing a thoracic brace to prevent kyphosis progression.

Case 3

A 13-year-old female child presented with low backache with right L5 radiculopathy for 1 year. She had bladder and bowel symptoms in the form of urinary retention and constipation. On MRI, a single extradural cyst opposite the L5 vertebral body was identified. Axial T2W MRI cuts revealed compression of the right L5 nerve root [Figure 3]A and B. Right L5 hemi-laminectomy with excision of the cyst was performed. Connection with dura was not found. Postoperatively, pain and radiculopathy were subsided but bladder and bowel habit improved incompletely. Now the patient is on self-clean intermittent catheterization. Postoperative MRI at 1-year follow-up revealed no recurrence of the cyst [Figure 3]C and D.
Figure 3: (Case 3) Preoperative mid-sagittal (A) and axial (B) images showing an extradural CSF intensity cystic lesion, compressing the existing right L5 nerve root. Postoperative images (C and D) showing no recurrence at the 1-year follow-up

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   Discussion Top


Demographics and pathogenesis

SEACs are a rare cause of spinal cord compression.[1],[2] These cysts most commonly occur in the middle to lower thoracic spine (65%) but have also been reported in the lumbar and lumbosacral (13%), thoracolumbar (12%), sacral (7%), and cervical regions (3%).[2],[3],[4] They are commonly located posterior to the cord at the thecal sac–nerve root sleeve junction, the dorsal midline, or the nerve root sleeve itself (85%). A few have been reported to extend into or through the neural foramen.[7]

According to the classification described by Nabors et al.[8] for spinal meningeal cysts, extramedullary cysts of the spinal canal can be divided into three main types:

  • Type 1: Extradural meningeal cysts that contain nonneural tissue subdivided into extradural cysts (Type 1A) and sacral meningoceles (Type 1B)


  • Type 2: Extradural meningeal cysts that contain neural tissue


  • Type 3: Intradural meningeal cysts.


  • All our cases belong to type 1A in this classification.

    Extradural arachnoid cysts develop from protrusions of arachnoid herniating through a small dural defect. The cysts have a pedicle in communication with the spinal subarachnoid space and, because of their origin, contain CSF.[3],[5],[6],[8] The cause of these cysts has not been determined definitively, although they most probably have a congenital origin.[9],[10] Familial occurrence, association with lymphedema and hereditary distichiasis, neurocutaneous melanosis, Marfan syndrome, and neural tube defects such as myelomeningocele and diastematomyelia have been reported in literature.[11] During the period of time, the connection between the cyst and subarachnoid space may be obliterated (case 3). Some may be acquired from trauma, infection, or inflammation.[12]

    Cyst enlargement can result in symptomatic spinal cord compression, though the cause of cyst enlargement with increasing age is debatable. The hypothesis currently accepted to explain the progressive enlargement of these arachnoid cysts involves two principal theories.[13],[14] Active (noncommunicating arachnoid cyst) and passive (ball–valve hypothesis) fluid-transport mechanisms have been hypothesized to explain enlargement of extradural meningeal cysts.[13],[14],[15] According to the first theory, an arachnoid cyst may enlarge even when it does not communicate with the subarachnoid space because of fluid production by the cells forming its wall. This could be the reason in our third case where no defect was found (noncommunicating arachnoid cyst). The second theory (the ball–valve hypothesis) postulates the existence of an anatomical communication functioning as a one-way valve between the subarachnoid space and the cyst, which allows the CSF to enter the cystic cavity (communicating cyst).[15] Failure of the histopathological examination to reveal an inner single-cell lining of extradural meningeal cysts or cells with a secretory capability makes most investigators now prefer the passive fluid-transport theory to explain the cause of cyst expansion via pulsatile CSF dynamics and the third mechanism of an osmotic gradient with or without valve-like mechanisms. This osmotic gradient theory alone explains the enlargement of the cyst in every case,[14] but identical biochemical and osmotic analysis of cyst fluid content itself puts a question to claims of this theory.

    Spinal arachnoid cysts generally develop in adolescents, and twice as many cases occur in male as in female patients.[2],[5] Thoracic cysts usually occur in young adolescents, whereas thoracolumbar and lumbar cysts usually appear in adults in the fourth decade of life.[2],[5],[6],[10] There are several reports in the literature of children presenting with spinal extradural cystic lesions; however, there are very few reports of a child presenting with multiple SEACs.[14],[16],[17] The youngest patient with multiple SEACs was reported by Srinivas et al.[17]

    In our series, two patients had multiple cysts. These lesions often arise dorsally and can partially protrude into the adjacent neural foramen. A single cyst can extend over several spinal segments or multiple cysts with separate dural defects, and communicating pedicles can compose one lesion.[16]

    Clinical presentation

    The location of the cyst within the spine and the severity of spinal cord and root compression affect the clinical presentation in the form of backache, extremity weakness, bladder symptoms, or paraspinal mass.[2],[5],[6],[10],[17],[18] Symptoms can be intermittent and exacerbated by Valsalva maneuvers, exercises, or gravitational positional forces.[19],[20] Intermittent enlargement of the cyst during strenuous activity could be the reason for bladder symptoms in our third case, though the cyst appears small in MRI pictures [Figure 3]. Remissions and fluctuation in symptoms have been reported in approximately 30% of cases.[14]

    Diagnostic studies

    The MRI is the investigation of choice for both diagnosis and delineation of the cyst dimensions. Identification of a sharp interface between the cyst and subarachnoid space related to the cyst wall and the surrounding dura mater, particularly on T2-weighted MR images, allows easy diagnosis of an extradural arachnoid cyst.[4],[7],[21] With all sequences, the signal within the lesion is iso-intense to CSF. The MRI can also show the extent of cord atrophy and myelo-malacia. Epidural fat capping of the lesion at its superior and inferior poles can be seen on sagittal T1-weighted MR images, which further suggests its extradural location and can be extremely useful to determine the multiplicity of lesions as in our first case [Figure 1]. Newer MRI flow studies using cinematic MRI techniques can identify a pulsating flow void to determine the location of the dural defect. Computed tomography (CT) myelography may also have a role in identifying the site of communication between the subarachnoid space and the cyst sac.[22]

    Although the prognosis of extradural meningeal cysts is favorable, only one-third of patients attain remission with complete recovery.[3],[5]

    In contrast, recent literature reported excellent outcomes, possibly due to wide availability of imaging modalities and use of a microscope, that clearly provide an edge for dural defect repair.

    Patient management

    Total cyst excision, obliteration of the communicating pedicle, and repair of the dural defect comprise the treatment of choice of the symptomatic lesions. Every attempt should be made intraoperatively to look for a dural defect, especially along the root sleeves, as its water tight closure is the single most important step to prevent recurrence.[3],[5],[17],[21] Valsalva maneuver can add to the localization of the dural defect and should be used after defect closure also to check for leak and any unidentified defect. The dural defect was not found intraoperatively in one of our cases (case 3). It is possible that during the period of time, the connection between the cyst and subarachnoid space may have been obliterated. These cysts can usually be dissected and elevated off of the dura with ease; however, in cases in which the cyst cannot be resected completely because of dense fibrous adhesion preventing safe separation of the cyst from the dura (especially posttraumatic, or post-inflammatory cysts), a wide marsupialization of the cyst can be performed by resecting the dorsal wall of the cyst and closing the dural defect.[23] Early postoperative imaging is also recommended in cases where a dural defect was not localized, to look for pseudomeningocele formation that may require urgent re-exploration.

    Postoperative kyphosis may be prevented by performing laminoplasty rather than laminectomy.[24] Nevertheless, there is paucity of evidence proving the superiority of laminoplasty to laminectomy.[25],[26] It needs not to be overemphasized that when possible, the surgical approach should proceed so as to address the dural defects directly in order to avoid extensive laminoplasty or laminectomy, to prevent postoperative spinal deformity. According to the reported cases in the literature, this is obviously not possible in all circumstances.

    Regarding the patient’s age (late puberty), it seemed rational to follow the patient both clinically and radiologically and to perform a fixation if a debilitating deformity ensued (fortunately no major disability occurred in any laminotomy patient who was controlled by brace, although the kyphosis progressed slightly for a period of time). Our recommendation, though, adheres to exploring all possibilities of performing laminoplasty in extensive lesions, especially in young patients, and we have not observed the progression of kyphosis in laminoplasty cases so far at the 3-year follow-up. Postoperatively, regular follow-up is needed to recognize the recurrence and development of kyphotic deformity and instrumentation can be done to prevent or correct it.


       Conclusion Top


    Symptomatic patients with SEAC should be treated as early as possible to gain maximum favorable results and to prevent refractory bladder and bowel involvement.

    Appropriate surgical procedure such as laminectomy/laminoplasty or laminotomy should be chosen depending on the location of the dural defect and extent of the lesion. To prevent kyphotic deformity, instrumentation can be done as per need and appropriate brace should be applied postoperatively.

    Watertight dural defect closure is a must, so thorough search intraoperatively should be done before closure.

    Regular follow-up is important regarding the possible recurrence and spinal deformity progression.

    Acknowledgement

    The authors want to acknowledge the support of the Department of Anesthesiology, Dr. RMLIMS in managing these challenging cases.

    Financial support and sponsorship

    Nil.

    Conflicts of interest

    There are no conflicts of interest.

    Authors’ contribution

    Dr. Deepak Kumar Singh: overall incharge, surgical management, and data collection.

    Dr. Satish Nayak: data collection and preparation of article.

    Dr. Neha Singh: article preparation, radiological analysis of images, and critical analysis of final draft.

    Dr. Vrihaspati Kumar Agrahari: data collection, statistical analysis.

    Dr. Anuj Chhabra: article preparation and evaluation of final draft.



     
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        Figures

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