Type I split cord malformation and tethered cord syndrome in an adult patient: A case report and literature review.

BACKGROUND: In a split cord malformation (SCM), the spinal cord is divided longitudinally into two distinct hemicords that later rejoin. This can result in a tethered cord syndrome (TCS). Rarely, TCS secondary to SCM presents in adulthood. Here, we present an adult female with Type I SCM resulting in TCS and a review of literature. CASE DESCRIPTION: A 57-year-old female with a history of spina bifida occulta presented with a 2-year history of worsening back and left leg pain, difficulty with ambulation, and intermittent urinary incontinence; she had not responded to conservative therapy. Magnetic resonance imaging (MRI) revealed a tethered cord secondary to lumbar type I SCM. The patient underwent an L1-S1 laminectomy for resection of the bony septum with cord detethering. At 2-month follow-up, the patient had improvement in her motor symptoms and less pain. In literature, 25 cases of adult-onset surgically managed SCM with TCS were identified (between 1936 and 2018). Patients averaged 37 years of age at the time of diagnosis, and 56% were female.
CONCLUSION: TCS can present secondary to SCM in adulthood and is characterized predominantly by back and leg pain.

INTRODUCTION

With routine use of folic acid supplementation, spinal dysraphism is rare in Western countries.[21] Split cord malformation (SCM), or diastematomyelia, describes a spinal cord divided longitudinally into two distinct hemicords that later rejoin. Symptoms typically reflect traction on the cord and stretch-induced ischemia.[1-7,9-11,13-15,18,20-28,30,32-35] TC in adults presents somewhat differently than in children, with predominant symptoms that include pain (81.6%), weakness (72.3%), and sensory disturbances (78.7%).[2] There are often cutaneous stigmata, foot deformity, or scoliosis not previously diagnosed in childhood. SCM has been categorized into two types: Type I SCM consists of two hemicords, each contained within its own dural tube and separated by a dura-sheathed rigid osseocartilaginous median septum [Figure 1]. Type II SCM consists of two hemicords housed in a single dural tube separated by a nonrigid, fibrous median septum.[8] Here, we present a 57-year-old female with Type I SCM and TC who underwent bony septum resection, and detethering with an adequate outcome, while also reviewing literature.

Figure 1:

Type 1 diastematomyelia, with bony septum highlighted in blue and absent spinous process shown by dotted line. Illustration by Erin D’Agostino, not previously published, permission granted.

CASE REPORT

A 57-year-old female with a history of spina bifida occulta and a left-sided clubfoot presented at age 56 with a 2-year history of worsening back and left leg pain, difficulty with ambulation, and intermittent urinary incontinence. On neurologic examination, she had 4+/5 strength in her LLE (iliopsoas, knee extension, knee flexion, dorsiflexion, and plantar flexion) with decreased distal left lower extremity strength (everters absent/loss EHL and decreased sensation). Deep tendon reflexes were 2+ throughout, and she had Babinski sign present on the left. MRI revealed a TC with SCM starting in the upper lumbar spine, becoming two separate dural sacs with a bony septum, and reconstituting into one dural sac/grouping of nerve roots ending in the sacrum [Figure 2]. The patient underwent an L1–S1 laminectomy utilizing neuromonitoring. The bony septum was excised, with spinal cord detethering/transection of the filum terminale. The patient was discharged 5 days after surgery to an acute rehabilitation hospital. 5 months postoperatively, she had significant improvement in dorsiflexion and plantar flexion, minimal back pain, no leg pain, and sphincter incontinence.

Figure 2:

Split cord radiographic and operative images. (a) Preoperative photograph of an area of hypertrichosis over the lower lumbar spine. (b) Sagittal T2-weighted magnetic resonance imaging (MRI) showing the division of the spinal cord above the dural division and bony septum. (c) T2-weighted axial MRI showed the split cord within a single dural sac. (d) Split cord within divided thecal sac. (e) Intraoperative imaging showing the split cord with associated fat and ectopic ganglion cells from the intradural lesion.

Operative procedure

Under total intravenous anesthesia, with electromyograph (EMG) and somatosensory evoked potential (SEP) monitoring, the patient underwent an L1–S1 laminectomy. Under an operating microscope, the bony septum was removed followed by a durotomy caudal to the split in the thecal sac. No expansile duraplasty was performed. The split cord occurred well before the division in the thecal sac and so was under no tension or compression.

Examination of the cord revealed fat and ectopic ganglion cells and nerve roots extending to the filum. These were resected, and the filum was detached, detethering the cord. The durotomy was closed with a running suture and a Valsalva was performed to verify a watertight closure. Intraoperative monitoring revealed just transient but nonsignificant changes in EMG and SEP.

DISCUSSION

A total of 24 case reports from 20 studies between 1936 and 2018 described SCM and TC diagnosed and surgically treated in adulthood. We included patients over the age of 18 years of age with symptomatic TC/SCM and who underwent surgical detethering. Preoperative status, surgical procedures, and outcomes are summarized [Table 1]. A more complete table reviewing the relevant literature was also generated [Table 2]. Surgical procedures included laminectomy, resection of a septum if present, and cord detethering. Patients were followed for an average of 1.61 years (standard deviation 1.77, range 0.03–7). For those who were initially symptomatic, postoperatively, 78.5% experienced reduced back pain (11/14), 69.2% reduced leg pain (9/13), 91.6% improved motor weakness (11/12), 80% improved sensation (9/11), and 66.7% improved bowel, bladder, or sexual dysfunction (4/6). Two of 19 patients with documented complications had a superficial infection and a cerebrospinal fluid leak.

Table 1:

A summary of demographics, presenting signs and symptoms, and surgical outcomes for patients with SCM and TC diagnosed and surgically treated in adulthood.

Table 2:

Literature review demonstrating presenting signs and symptoms, imaging findings, operative procedures, and follow-up status of patients with adult presentation of diastematomyelia with tethered cord syndrome who underwent operative intervention.

Infrequently, tethered cord syndrome (TCS) secondary to SCM presents in adulthood.

SCM is reported to account for 10%–38% of adult TC diagnoses.[16,17,19,21,26,27,31] Two subsets of patients with SCM present in adulthood – those with SCM diagnosed in childhood who experience recrudescent symptoms and those who are first diagnosed with SCM in adulthood.[26] Our patient falls into this second category. In adulthood, presentation differs somewhat, with predominance of back and leg pain rather than with overt skeletal abnormalities or with progressive urological or orthopedic dysfunction.[12,15,26,32,34] Our patient presented primarily due to back and leg pain. In literature, 76% of patients present with back pain and 72% with leg pain. Our patient was also noted to have intermittent incontinence. In literature, 36% of patients experience bowel, bladder, or sexual dysfunction. Our patient presented with cutaneous stigmata, much like 56% of patients in literature. On imaging, our patient had a Type I SCM in the lumbar spine. In literature, 41% of patients with SCM present with Type I SCM and 80% of SCMs are found in the lumbar spine.

Adult TC surgical results

In the adult population, the general consensus is that surgery is appropriate if neurologic deficits exist or symptoms are progressive.[21] In one review of 368 adult patients with TC who were operated (67 of whom had SCM), 83% experienced improvement in pain symptoms, 43% improvement in sensory deficits, 59% improvement in motor deficits, and 46% improvement in incontinence.[2] Predictors of poor outcome in the review included lipomyelomeningocele, previous surgery, rapid motor deterioration before operation, long delay to diagnosis, and, notably, SCM.[2] A smaller study of adults with TCS without SCM demonstrated similar improvements but with greater improvement in leg weakness.[12] One study found that of 24 patients with SCM and neurologic deficits who underwent surgery, 23 demonstrated neurologic improvement.[29]

Complications of adult detethering procedures

Adult patients who undergo detethering appear to have higher complication rates than pediatric patients but lower rates of retethering,[17] with 16% of adult patients demonstrating retethering over 8 years compared to 52% of pediatric patients within 5 years.[16] In our review of adult-onset SCM with TCS, surgery – which comprised laminectomy, resection of a septum if present, and detethering with sectioning of the filum terminale – resulted in improved weakness (92%), sensory dysfunction (80%), back pain (79%), leg pain (69%), and bladder, bowel, or sexual dysfunction (67%). Our patient underwent an uncomplicated L1–S1 laminectomy for the resection of bony septum and cord detethering, and at 2-month and 5-month follow-up reported improved motor symptoms and reduced pain.

CONCLUSION

TCS secondary to SCM rarely presents in adulthood. The adult presentation is primarily characterized by back and leg pain. Trauma on a macro/micro scale may result in increased traction on the cord, and progressive vascular compromise resulting in the symptom onset in adulthood. Surgical treatment is appropriate and effective when neurological symptoms are present.