Spinal epidural arachnoid cyst
Neurosurgery Department, University General Hospital of Alicante, Foundation for the Promotion of Health and Biomedical Research in the Valencian Region (FISABIO), Alicante, Spain
The pathologic history of the patient is essencial to establish the etiology.
Extradural arachnoid spinal cysts are unfrequent lesions that are associated with spinal trauma, surgery and less frequently with congenital anomalies. Most cases are sporadic; however, three familial cases have been reported, suggesting genetic etiological factors 1) 2).
Cervicothoracic extradural arachnoid cysts and obstetric brachial plexus palsy has been reported in two patients.
The first patient is a 9-month-old boy with left obstetric brachial plexus palsy that developed bilateral leg weakness at 6 months of age owing to compression of the spinal cord by a C6 to T8 left cervicothoracic extradural arachnoid cyst. The second patient is a 3-year-old girl with bilateral brachial plexus palsy and spastic paraparesis who had magnetic resonance imaging at 3 days of age that showed intraspinal cord injury and a cervicothoracic extradural arachnoid cyst compressing the spinal cord. Miravet et al. believe that this association of cervicothoracic epidural arachnoid cysts and obstetric brachial plexus palsy in these patients was causal and recommend that the possibility of a cervicothoracic epidural arachnoid cyst be considered in patients with brachial plexus palsy and evidence of spinal cord injury 3).
All familial cases are associated with lymphedema-distichiasis syndrome (LDS), whose causal gene is FOXC2. However, FOXC2 mutation analysis has been performed in only 1 family, and no mutation analysis has been performed on sporadic (non-familial) SEACs.
Seven sporadic SEDAC subjects had no FOXC2 mutations, no symptoms of LDS, and showed differing clinical characteristics from those who had FOXC2 mutations, suggesting that other gene(s) besides FOXC2 are likely to be involved in SEAC 4).
Idiopathic spinal epidural arachnoid cysts (SEACs) are relatively rare lesions with diverse clinical manifestations depending on the affected spinal region and nerve roots.
Of 15 consecutive patients with idiopathic SEACs, 14 underwent surgical treatment at the Beijing Tiantan Hospital between January 2008 and July 2013. Case histories, clinical presentations, imaging findings, operative findings, and surgical outcomes were reviewed.
Of the 15 patients, 5 were children (median age, 13 years) and 10 were adults (median age, 35 years). The male-to-female ratio was 4:1. The median disease duration was 1 year in children and 4 years in adults. The most common manifestations were progressive paraparesis (73.3 %) and radiculopathy (66.7 %). All pediatric lesions affected thoracic segments, while 80 % of adult lesions affected lumbar segments. Fourteen patients underwent microsurgical treatment, with cyst excision in nine (combined with fistula closure in four) and partial cyst excision in five (with fistula closure in three). No recurrences were observed during follow-up (average of 23 months). Excellent outcome was achieved in six cases, good outcome in four, fair in two, and poor in two.
Idiopathic SEAC mainly affect the thoracic segments in children and the lumbar segments in adults, and often results in progressive paraparesis and radiculopathy. Early surgical intervention is suggested for progressive symptomatic patients to restore neurological function 5).
The clinical manifestations are similar to those seen with other compressive spinal cord lesions.
Magnetic resonance techniques allow to diagnose correctly this pathology and to define its topographic situation since 1989 6).
Kinematic magnetic resonance imaging study demonstrated that pressure changes which occur in the extradural space as well as in the arachnoid cyst might cause spinal cord compression and result in intermittent exacerbation of symptoms 7).
Total excision of EACs may have little benefit in terms of cyst recurrence and clinical outcome. The procedure for EAC resection carries a risk of complications such as kyphosis. If EAC resection is performed, Lee et al. suggest that a tailored short-level laminotomy be used to allow for the repair of dural defects. Particularly in patients with small EAC, a partial hemilaminectomy with dural defect repair may be a possible method to reduce complications 8)
Two children with three spinal extradural arachnoid cysts and each cyst protruded from a separate dura defect. In both patients, plain radiographs demonstrated widening of the interpedicular distance, which suggested progressive widening of the spinal bony canal. Limited laminectomy was performed to remove the intraspinal cysts. Separate dura defects, the apparent predisposing factors, were also found and repaired. The patients completely recovered neurologically. Radical cyst removal and dura defect closure are the surgical intervention of choice in patients with symptomatic extradural arachnoid cyst 9).
Kadono et al. report a case of posttraumatic symptomatic spinal epidural arachnoid cyst (EAC) with lumbar disc herniation. A 22-year-old man experienced back pain and sciatica after a traffic accident. Neurological examination revealed a right L5 radiculopathy. Magnetic resonance imaging demonstrated a cystic lesion at the L3 to L5 level and an L4-5 disc herniation; computed tomography myelography showed that the right L5 root was sandwiched between the cyst and the herniation. A dural defect was identified during surgery. The cyst was excised completely and the defect was repaired. A herniation was excised beside the dural sac. Histology showed that the cyst wall consisted of collagen and meningothelial cells. Postoperatively the symptoms resolved. Lumbar spinal EACs are rare; such cysts may arise from a congenital dural crack and grow gradually. The 6 cases of symptomatic lumbar EAC reported in the literature were not associated with disc herniation or trauma. In this case, the comorbid disc herniation was involved in symptom progression. Although many EACs are asymptomatic, comorbid spinal disorders such as disc herniation or trauma can result in symptom progression 10).
A 35 years old man who has a medical history of penetrating spinal trauma two years ago. In that instance he suffered an unilateral spinal cord section at D2-D3 level with the corresponding Brown Sequard syndrome. A small wound was detected at the skin dorsal level and it was closed without difficulties. At the beginning, he improved his motor right leg function with rehabilitation and vitamins. After two years of good recovery he came to our hospital suffering a neurological deterioration of six months of evolution. The physical examination revealed an spastic paraparesis. Magnetic resonance was performed demonstrating a cystic extradural collection compressing the spinal cord at D3-D4 level. Surgical decompressive treatment allowed to excise the cyst and it was possible to define a dural tear that was closed successfully. The outcome was good with restoration of the initial motor function that he had after the spinal trauma.
Surgical management of postraumatic epidural arachnoid spinal cyst allows to detect the meningeal tear and to close it, which is highly effective on these kinds of lesions 11).
A 9-year-old boy with a slowly progressive spastic paraparesis. MRI revealed dorsal epidural arachnoid cyst extending from T7 vertebral body to L1 body producing marked cord compression. In order to save the child from a long segment laminectomy or laminoplasty, a new minimally invasive technique was devised. In this technique L1 laminectomy was performed under local anaesthesia, and the cyst was communicated to thecal sac by making an interconnecting stoma. The author named this procedure as cystothecostomy. There was gradual neurological recovery after the procedure 12).
A 25-year-old man who presented with progressive cauda equina syndrome. Neuroimaging revealed two neighboring sacral epidural cysts. The cysts were completely removed via a sacral S1-4 laminectomy; no communication with the subarachnoid space could be found. The patient’s postoperative course was uneventful. He experienced progressive improvement and, finally, complete resolution of symptoms and no recurrence of the cyst. Nabors Type I sacral epidural arachnoid cysts are rare; in some cases their origins and the mechanism by which they cause deterioration in the patients’ clinical condition are debatable. Findings in the present case support the idea that some of these cysts are noncommunicating but progressive in their clinical presentation 13).
Preoperative magnetic resonance imaging (MRI) myelography scans demonstrated a dural defect in a 50-year-old man with an epidural arachnoid cyst who had a 29-year history of untreated weakness and numbness both lower limbs.
MRI scans showed a dorsal intraspinal extradural cystic lesion at the level from Th11 to L1. Although preoperative cine-MRI scans failed to display the dural defect, an MRI myelography scan showed cerebrospinal fluid in the subarachnoid space containing a cyst.
The site of shunting between the subarachnoid space and the cyst was visualized as a pulsating flow void to the right of Th12. They removed the cyst wall and closed the dural defect via laminectomy.
Because the preoperative MRI myelography scan correctly identified the existence and location of the dural defect, they conclude that MRI myelography is helpful for detecting dural defects in patients with epidural arachnoid cysts 14).
Takahashi et al. describe the case of a high cervical, intradural extramedullary cyst located anterior to the spinal cord in a 13-year-old boy. The lesion was fenestrated percutaneously by using real-time magnetic resonance (MR) imaging guidance and a local anesthetic agent. The patient’s symptom, severe exercise-induced headache, immediately resolved after treatment. Nine months later, complete disappearance of the cyst was confirmed on MR imaging and computerized tomography myelography. Magnetic resonance imageing-guided fenestration can be considered a minimally invasive option for intradural cystic lesions 15).
The case of 16-year-old boy with a spinal extradural arachnoid cyst is presented. An extradural arachnoid diverticulum extending from T10 to L1 was excised totally with hemilaminectomy. Surgery caused prompt improvement of the neurological deficit 16).
An extradural arachnoid cyst of the thoracic spine was diagnosed and operated in a 39 year-old woman with a history of two regressive attacks of spastic paraplegia during a 19 year-period. The diagnosis was established by magnetic resonance imaging and myeloscan, which demonstrated the cyst and its consequences on the spinal cord and the spine 17).