Scimitar sacrum with anterior meningocele: A case report

A 29-year-old man with cerebral palsy presented with complaints of breathlessness and was diagnosed with ARDS (acute respiratory distress syndrome). He had no history of prior admissions. After a few days, he complained of abdominal pain. Bedside ultrasound showed mild free fluid in the abdomen.

The plain AP radiograph of the abdomen shows lumbar scoliosis with convexity to the right and spinal dysraphism at the S1–S2 level. There is a defect of the sacrum involving the right inferior segment (Figure 1). An unenhanced CT scan of the abdomen (due to raised serum creatinine) confirms the findings on the radiograph. There is segmentation anomaly of the sacrum with a defect in the right half of the sacrum. There is ventral herniation of thecal sac, leading to a presacral mass measuring approximately 3.5x3cm. There was no fat-containing lesion or any defect in the skin and subcutaneous tissue posteriorly. There was bladder wall thickening with mild hydronephroureterosis and a few tiny calculi in both kidneys.

Scimitar sacrum is a term for the sickle-shaped sacral defect which is associated with an anterior meningocele. Together with the presacral mass and anorectal malformation, it forms a part of the Currarino triad [1]. The presacral mass is usually an anterior meningocele, a teratoma, or an enteric cyst [1]. The embryological basis for these entities is abnormal endo-ectodermal adhesions and notochordal defects. The developing notochord induces the formation of the vertebral body from the somites, which then separates the closely related neural ectoderm and the endoderm, which forms the future gut [1]. Persistent adhesions may cause the notochord to split or move laterally, resulting in non-fusion of the vertebrae anteriorly. Alternatively, early splitting of the notochord may result in the endoderm being intimately related to the neural tube [1]. Acquired cases may be seen in Marfan syndrome or neurofibromatosis [2].

Clinical presentation may vary from asymptomatic to acute emergencies secondary to infection [3]. Most of the patients present in childhood. In adults, they are detected incidentally on imaging done for some other purpose, as was seen in our case. On probing, these patients might have a history of chronic constipation. There might be pressure symptoms on the adjacent organs and the sacral nerve roots [4]. Apart from constipation, the patients might experience low back pain, urinary incontinence, or retention. Few patients might have headaches and episodes of meningitis [4].

The plain abdominal radiograph shows the classic scimitar sacrum, indicating an underlying presacral mass [2,5]. Ultrasound is the initial modality ordered which shows a cystic lesion in the presacral region. In cases of teratoma, there is the presence of fat and calcification. It is also useful in ruling out ovarian pathologies as the origin of these lesions [4]. It, however, does not delineate the relation with the spinal canal. CT also has a limited role. It shows the bony defects with anatomical relations of the presacral mass. CT myelography plays an important role in depicting communication with the spinal canal. MRI is the gold standard for characterisation and surgical planning [2].

Asymptomatic patients are managed conservatively. Our patient was advised to follow up since it was detected incidentally. Even when asymptomatic, these lesions may pose an obstetric complication. Surgical resection (commonly via the posterior approach) is the mainstay of treatment for symptomatic patients [3,4,6].