Surgical treatment for recurrent thoracic ventral intradural arachnoid cyst secondary to tuberculous meningitis: a case report

Abstract

Introduction

Spinal intradural arachnoid cysts (SIACs) are rare spinal entities that are categorized as primary or secondary pathologies. Secondary cysts can arise from various traumatic or inflammatory causes including subarachnoid hemorrhage, intrathecal injection or surgery, and infectious meningitis/arachnoiditis. Only a few cases of SIAC secondary to tuberculous meningitis have been previously reported, without details of the surgical treatment.

Case presentation

A 27-year-old woman diagnosed with tuberculous meningitis developed myelopathy caused by thoracic ventral SIAC and intradural abscess. The patient underwent abscess evacuation and cyst fenestration; however, cyst recurrence occurred. The 2nd surgery consisted of cyst resection via a posterolateral approach with expansive duraplasty and spinal arthrodesis. Re-recurrence occurred, and at the 3rd surgery, cyst-subarachnoid bypass was performed. One year after the 3rd surgery, the myelopathic symptoms recovered, and MR images demonstrated a decreased cyst size.

Discussion

Here, we report a rare case of recurrent thoracic SIAC secondary to tuberculous meningitis and arachnoiditis. Simple fenestration is associated with a high risk of recurrence in this pathology. Ventrally located thoracic cysts can be approached with posterolateral approach with pedicles resected followed by instrumented arthrodesis. Even in cases involving gross total resection of the cyst wall, there is a risk of recurrence. In such cases, cyst-subarachnoid bypass with a large-diameter tube can be effective.

Introduction

Spinal intradural arachnoid cysts (SIAC), classically classified as Nabors type III meningeal cysts [1], are rare spinal entities that are further categorized as primary or secondary pathologies. Secondary cysts can arise from various traumatic or inflammatory causes including subarachnoid hemorrhage, intrathecal injection or surgery, and infectious meningitis/arachnoiditis [2]. Only few case reports have demonstrated SIAC secondary to tuberculous meningitis [3, 4]. None of these describe surgical treatment strategy in detail.

Here, we report a rare case of recurrent thoracic ventral SIAC secondary to tuberculous meningitis and arachnoiditis, who required three times surgery, and also illustrate an effective salvage technique by cyst-subarachnoid bypass.

Case presentation

A 27-year-old woman from India presented with disorientation, fever, headache, urinary retention, and bowel incontinence. Polymerase chain reaction of the spinal tap was positive for Mycobacterium tuberculosis. Antituberculosis agents were administered. Although her general appearance improved after medical treatment, neurological deficits in her lower extremities gradually progressed. Spinal magnetic resonance imaging (MRI) revealed an arachnoid cyst on the ventral side at the T7-9 levels as well as intradural abscesses on the dorsal side at T5-6 (Fig. 1A–D). A syrinx was not observed. In the follow-up MRI evaluations, the intradural abscess enlarged despite the use of anti-tuberculous medications, and subsequently surgical intervention was chosen.

Fig. 1. Preoperative and intraoperative findings for the first surgery.

A and C: Preoperative T2-weighted magnetic resonance (MR) images (white arrow indicates the intradural arachnoid cyst). B and D: Preoperative enhanced T1-weighted MR images (white arrow indicates the intradural abscess). E: Intraoperative picture showing a cream-colored intradural abscess.

1st surgery; abscess evacuation and cyst fenestration

We performed intradural abscess drainage at T5-6 (Fig. 1E) and arachnoid cyst fenestration at T7-8. After surgery, her neurological deficits improved, and she became ambulant. Postoperative spinal MRI revealed shrinkage of the arachnoid cyst and disappearance of the intradural abscess. She was transferred to the affiliated rehabilitation center.

2nd surgery; cyst resection, duraplasty, and spinal arthrodesis

Two months after the continuation of physical therapy, the myelopathic symptoms gradually worsened despite the ongoing anti-tubercular medication. A follow-up MRI was performed and showed recurrence of the arachnoid cyst with significant spinal cord compression associated with syrinx formation, while the intradural abscesses disappeared (Fig. 2A, B). Therefore, we decided to perform a 2nd surgery. The 2nd surgery intended cyst resection with expansive duraplasty and spinal arthrodesis via a posterolateral approach. After the standard posterior exposure, segmental pedicle screw placement was performed at T4-11, except for right T7-9 followed by T5-9 wide laminectomy and T7-9 pediculectomy to approach the ventral cyst posterolaterally. We confirmed cyst formation on the ventral side of the dura at the T7-9 level using ultrasonography. Figure 2C–I shows the intraoperative microscopic images. The dura was then opened on the right side. We dissected the dentate ligaments and the T7/T8 right nerve roots, gently retracted the spinal cord to the left side and identified an arachnoid cyst on the ventral side. We performed gross total resection on the cyst wall. The spinal cord parenchyma and dura mater were highly adherent to each other. After adhesiolysis and cyst wall resection, expansive duraplasty was performed using a fascia graft from the tensor fasciae latae (2 cm × 8 cm). Finally, rods were engaged on the screws and spinal fixation was completed (Fig. 3A, B). Postoperatively, the lower extremity muscle weakness gradually improved. Postoperative MRI showed cerebrospinal fluid flow inside the arachnoid cyst space as well as beneath the expanded dura (Fig. 3C, D).

Fig. 2. Preoperative and intraoperative findings for the second surgery.

A, B T2-weighted magnetic resonance (MR) images before the 2nd surgery (white arrow indicates the cyst). C Intraoperative photograph demonstrating adhesiolysis on the dorsal aspect of the cord. Cutting right T7 nerve roots (D) and cyst exposure behind the cord (E). Cutting the T8 root (F), resecting the cyst wall (G), and post-cyst resection (H). I Duraplasty with fascia lata.

Fig. 3. Postoperative findings for the second surgery.

A, B Post-2nd surgery plain radiographs. C, D Post-2nd surgery magnetic resonance (MR) images.

3rd surgery; cyst-subarachnoid bypass

Two months after the 2nd surgery, the myelopathic symptoms worsened again. MRI showed a re-recurrence of the cyst with significant spinal cord compromise (Fig. 4E). The 3rd surgery was performed. Using the same posterolateral approach as in the 2nd surgery, the right side of the dural matter at T7-9 was exposed. Using an ultrasonic guide, a silicon tube with 3.0 mm diameter was inserted inside the cyst, and CSF flow was confirmed from the counterpart tip of the tube (Fig. 4A, B, D). The counterpart was placed inside the caudal subarachnoid space at T10-11 (Fig. 4C). The tube was sutured to the surrounding soft tissue at three different locations to prevent migration. One year after the 3rd surgery, the MR image showed improvement of spinal cord compromise with a patent tube located inside the cyst (Fig. 4F). The neurological deficit completely resolved, and the patient became ambulant without a cane. The anti-tubercular medication was continued for 12 months after the initial diagnosis. Figure 5 summarizes the three surgeries performed in this case.

Fig. 4. Intraoperative and postoperative findings for the third surgery.

Third surgery intraoperative photographs demonstrating a 3.0-mm bypass tube placement (A), the proximal tip is inserted into the cyst with an ultrasonic guide (B, D), and the distal tip is inserted into the subarachnoid space at the T10-11 level (C). E Pre-3rd surgery magnetic resonance (MR) image showing enlarged cyst with significant cord compromise. F One-year post-3rd surgery MR image showing a patent tube inside the cyst (white arrow) with decreased cyst size.

Fig. 5. Schematic summary of the surgical procedures.

1st surgery; abscess evacuation and cyst fenestration. 2nd surgery; cyst resection, duraplasty, and spinal arthrodesis. 3rd surgery; cyst-subarachnoid bypass.

Discussion

Surgical treatment for SIACs includes fenestration, shunting, and cyst resection [2]. Fenestration is the most commonly used technique and has been reported to provide good outcomes for primary cysts. However, for secondary cysts, effect of fenestration alone was limited and lead to high rate of recurrence likely due to presence of adhesive arachnoiditis [5]. Similarly, cyst resection has demonstrated favorable outcomes with a minimal recurrence rate for primary dorsal cysts [5]; however, for the secondary cysts, especially those ventrally located, total resection of the cyst wall is almost impossible via the posterior approach and poses a high risk of spinal cord damage in the setting of adhesive arachnoiditis. As in our case, the posterior aspect of the spinal cord is highly adhesive to the dura mater, and durotomy should be performed through the lateral side (directly to the cyst) to avoid incidental myelotomy. Various shunting procedures have been reported, including cyst-subarachnoid shunt [6], cyst-peritoneal shunt [7], and cyst-pleural shunt [8].

The rationale for the surgical procedure used in this case is as follows. In the 1st surgery, the primarily responsible region was thought to be an intradural abscess at T5-6. Therefore, we focused on evacuation and irrigation of the abscess during the index surgery, with a simple fenestration chosen for the cyst.

In the 2^nd surgery, we attempted total resection of the cyst as definitive therapy. Using the posterolateral approach with the three right pedicles resected, we were able to approach the lateral side of the dura. By dissecting the dentate ligament and the two nerve roots, we resected the cyst wall while minimizing spinal cord retraction. Direct repair of the dura after cyst resection was tight and could aggravate spinal cord compromise; therefore, we chose to add expansive duraplasty using fascia lata. Spinal instability after multiple pediculectomies was anticipated; therefore, we performed spinal arthrodesis at–T4-11. From a retrospective perspective, the bypass technique (described below in the 3^rd surgery) should have been added at this 2nd surgery as a re-recurrence could have been expected in view of possible suboptimal cyst wall resection or new septum formation from severe arachnoiditis.

In the 3rd surgery, CSF diversion was required. We modified the subarachnoid-subarachnoid bypass procedure previously reported for adhesive arachnoiditis by Tachibana et al. [9] The bypass procedure, using a large diameter tube with 3.0–4.0 mm, has an advantage over shunt procedures using small tubes. Use of a larger tube reduces the risk of postoperative tube occlusion. Although the cyst-peritoneal/pleural shunts demonstrated good outcomes in a few case reports [7, 8], we believe that cyst-subarachnoid diversion remodels the physiological CSF flow system and does not require adjustment of the flow amount. In addition, the risk of infectious complications due to shunts is low. The entry point at the distal end of the bypass tube should be a level where dorsal CSF flow is completely patent on the MR image. Epidural fibrosis and scarring significantly complicate revision spinal surgeries, especially in cases involving multiple operations. The presence of extensive epidural scar tissue and dural adhesions increases the risk of unintentional durotomy, which may go unnoticed during surgery. Although it is favorable to establish a clear separation between the scar tissue and the dura mater, this may be practically unfeasible. In our case, we first identified the bony landmarks (residual laminae and pedicles) and then separated the dura while retaining some surrounding scar tissues when approaching the posterolateral side of the cyst, which helped avoid an unintentional dural tear. When inserting a tube into the cyst, the use of an ultrasonic guide was effective in confirming the tube’s position.

Conclusions

Fenestration is associated with a high risk of recurrence in the SIAC secondary to tuberculous meningitis. Ventrally located thoracic cysts can be approached with posterolateral approach with pedicles resected followed by instrumented arthrodesis. Even in cases involving gross total resection of the cyst wall, there is a risk of recurrence. In such cases, cyst-subarachnoid bypass with large-diameter tube can be effective.

Author contributions

YS was responsible for writing the report, updating reference lists, organizing figures, revising the report. TS was responsible for writing the report, updating reference lists, organizing figures, revising the report, performing the surgical procedure described. BO was responsible for revising the report, updating reference lists, assisting with the surgical procedure described. SM was responsible for revising the report, supervision.

Competing interests

The authors declare no competing interests.

Ethical approval

This study was approved by our institutional review board (No. R2901).

Informed consent

Written informed consent was obtained for the publication of this report and accompanying images from the patient’s parent.

Supplementary information

The online version contains supplementary material available at 10.1038/s41394-024-00650-5.