A 50-year-old female with a background of Marfan syndrome, blindness due to dislocation of lens and previous David procedure for ascending aortic aneurysm, presented with back pain and urinary symptoms.
Plain film imaging showed degenerative changes of the lumbar spine with posterior vertebral scalloping of the lumbo-sacral vertebral bodies [Figure 1].
Computed tomography (CT) was performed as follow up imaging for the aortic surgery, which demonstrates the posterior vertebral scalloping with widening of the right anterior sacral foramina and a fluid filled pre sacral mass [Figure 2].
Magnetic resonance imaging (MRI) of the whole spine was performed, which revealed a large anterior sacral meningocoele measuring 11cm (T) x 9cm (AP) x 9cm (CC). It extends through the right anterior sacral foramen at S2-S3 level [Figure 3]. This displaces the uterus and bladder anteriorly [Figure 4]. Dural ectasia causing scalloping of the vertebral bodies in the lumbosacral spine was also demonstrated at other levels.
Herniation of dura and arachnoid mater from the sacral spinal canal anteriorly into the pelvis leads to anterior sacral meningocoeles (ASM) [1].
Causes are multifactorial [1, 2]
• Congenital sacral or collagen defects e.g. Marfan syndrome
• Degenerative changes of the spine causing enlarged intervertebral foramen
• Traumatic injury with nerve root avulsion
• Iatrogenic injury
Congenital ASM usually occur in 1/1000 births [3, 4], with female predominance (4:1) [5, 6]. Initially asymptomatic, they can enlarge in later life presenting with pressure effects, such as back pain or sciatica, urinary incontinence and constipation [1, 5].
Patients with connective tissue disorders, such as Marfan syndrome and neurofibromatosis, have a higher incidence of ASM and associated abnormalities i.e. spina bifida and imperforate anus [5, 6]. Marfan syndrome is associated with abnormal fibrillin-1 production leading to fragmentation and disorganisation of the elastic fibres [7]. The weakened dural sac is more likely to stretch and enlarge due to hydrostatic pressures of pulsatile cerebrospinal fluid and gravity. ASM commonly occurs in the L3 to S1 region [8, 9]. As the patient ages there is enlargement of the dural sac with thinning of the pedicles and laminae, and widening of the neural foramina, leading to posterior vertebral scalloping [6].
Initial investigation by plain film radiography can demonstrate posterior vertebral scalloping or bony deformity of the sacrum, such as the scimitar sacrum where there is absence of one side of the sacrum at one or more level [6]. Further delineation of bony anatomy can be demonstrated by computed tomography (CT). However, magnetic resonance imaging (MRI) is the modality of choice providing detail of the ASM, nerve roots and complications such as tethered cord, tumours or lipomas. Sometimes, myelography can establish the communication between ASM and subarachnoid space, especially if the connection is narrow and not seen on the CT/MRI.
There is controversy between conservative or surgical management of ASM’s. Some studies suggest conservative management especially when asymptomatic, however others claim early surgical treatment is more successful with fewer complications [5, 8]. Surgery aims to obliterate the communication between ASM and subarachnoid space, releasing the nerve roots [6].
Surgical methods include:
• Open posterior approach, with sacral laminectomy to tie off the ASM neck [8].
• Open anterior transperitoneal approach usually for large ASM, with other abdominal abnormalities [8].
• Laparoscopic surgery for narrow ASM [10].
• Lumbo-peritoneal shunts are placed in patients with a high pressure ASM and surgery is unsuccessful [2].
Anterior sacral meningocoele
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1. Mild “indentation” sign of the posterior vertebral margin can be seen on the lateral lumbar X-ray (thinning of the posterior cortex and protruding posterior vertebral outline), indicating changes in the posterior aspect of the vertebral body.
2. On CT imaging at the sacral level, a relatively large cystic lesion is observed in the anterior pelvis, possibly communicating with the sacral canal. The local bone appears expanded, thinned, and morphologically altered.
3. MRI in sagittal and axial sequences demonstrates that this cystic structure shows CSF-like signal characteristics (low signal on T1, high signal on T2). A narrow channel is seen connecting it to the dural sac, suggesting a protrusion from the subarachnoid space.
4. The cyst is well-demarcated from the surrounding soft tissue, with no obvious evidence of tumors or other soft tissue masses. The patient complains of low back pain and urinary-related symptoms, potentially linked to compression of peripheral nerves or tissues by the cystic lesion.
1. Anterior Sacral Meningocele:
- The patient has a history of Marfan syndrome, a connective tissue disorder often associated with dural ectasia, spinal deformities, or arachnoid cyst formation.
- MRI reveals a cystic lesion with a signal similar to CSF, which is connected to the subarachnoid space.
- Considering the symptoms (back pain, urinary issues) and imaging (sacral bone changes, etc.), this diagnosis is highly suspected.
2. Tarlov Cyst (Perineural Cyst):
- These are also diverticula of the dura mater or nerve root sheath but are typically located on the posterior side of the sacral canal and associated with nerve roots.
- They are usually smaller in size, and when symptomatic, often result from nerve root compression.
- Currently, imaging findings more closely match the location and morphology of an anterior sacral meningocele, making a Tarlov cyst less likely.
3. Other Pelvic Cystic Lesions (e.g., cystic tumors, ovarian cysts, or lymphangioma):
- Based on the atypical morphological and signal characteristics and the apparent communication with the subarachnoid space, these diagnoses are less likely.
Taking into account the patient’s Marfan syndrome history, imaging findings (changes at the posterior margin of the sacral vertebra, a large cystic structure communicating with the subarachnoid space), and clinical symptoms, the most likely diagnosis is: Anterior Sacral Meningocele.
1. Treatment Strategies:
- Conservative Follow-up: If the cyst is small, symptoms are mild, or there is no clear nerve compression, regular follow-up is recommended to monitor disease progression.
- Surgical Intervention: For significant symptoms (e.g., persistent low back pain or urinary dysfunction), large cysts, or clear nerve-related signs, surgery should be considered. The goal is to close the communication between the cyst and the subarachnoid space and decompress neural structures. Options may include a posterior sacral canal approach or laparoscopic repair.
- Adjunctive Measures: If intracranial pressure is elevated or surgical repair fails, a cerebrospinal fluid (CSF) shunt (e.g., lumboperitoneal shunt) may be considered.
2. Rehabilitation / Exercise Prescription:
Goals: To safely maintain or improve core muscle strength, protect spinal stability, and help the patient maintain daily functional capacity. Patients with Marfan syndrome often have more fragile skeletal and connective tissues, so exercise intensity and pace must be carefully controlled.
- Initial Stage (Preoperative or Conservative Follow-up):
• Frequency: 3–4 times per week
• Intensity: Low to moderate, avoiding excessive load or high-impact activities
• Duration: 20–30 minutes per session, including warm-up and cool-down
• Type: Core strength exercises in a seated or supine position (e.g., bridge exercises, small-range supine leg lifts to avoid overstretching), gentle swimming, or aquatic exercises
• Progression: As long as pain and neurological symptoms are manageable, gradually incorporate more core stabilization exercises such as planks (starting from 10 seconds and increasing to 30 seconds or more), under medical or therapist guidance.
- Postoperative or When Condition Is Relatively Stable:
• Frequency: 3–5 times per week
• Intensity: Mainly moderate; gradually increase according to postoperative recovery and medical advice
• Duration: 30–45 minutes per session, including adequate warm-up and stretching
• Type: Combine core stability training with light to moderate aerobic activities, such as walking on level ground, elliptical training, or slow-paced cycling
• Progression: After assessment by a physician or rehabilitation therapist, add minimal resistance training (resistance bands or light dumbbells). Emphasis on core strengthening remains crucial.
- Safety Precautions:
• Avoid high-impact, aggressive twisting, or excessive stretching to prevent additional spinal or soft tissue injuries.
• Seek medical attention promptly if low back or sacral pain worsens significantly, radicular pain develops, or urinary function changes occur.
• Adjust intensity based on the patient’s cardiopulmonary status and skeletal condition as needed.
Disclaimer: This report is based on the existing medical history and imaging data for reference purposes only and does not replace face-to-face consultation or professional medical advice. If you have any concerns, please consult a specialist and undergo further evaluation.
Anterior sacral meningocoele
