Outcome of untethering for symptomatic spina bifida occulta with lumbosacral spinal cord tethering in 31 patients: analysis of preoperative prognostic

Jen-Ho Tseng, Meng-Fai Kuo, Yong Kwang Tu, Ming-Yuan Tseng Outcome of untethering for symptomatic spina bifida occulta with lumbosacral spinal cord tethering in 31 patients: analysis of preoperative prognostic factors The Spine Journal, Volume 8, Issue 4, July-August 2008, Pages 630-638

BACKGROUND CONTEXT: The most important goal for treating symptomatic lumbosacral spinal cord tethering is early untethering.

PURPOSE: To investigate preoperative symptoms that may have affected the outcome.

STUDY DESIGN: Patients with or without improvement and with or without favorable outcome after untethering were compared retrospectively by chart and image review.

PATIENT SAMPLE: Thirty-one patients (age between 2 days to 25 years) with spina bifida occulta and symptomatic cord tethering were analyzed. Presenting symptoms (neurological deficits, urological dysfunction, and lower limb deformities) were assessed before and after untethering.

OUTCOME MEASURES: Favorable outcome was defined as complete relief of symptoms or mild symptoms whereby patients are able to look after their own personal care without assistance. Unfavorable outcome was defined as moderate or severe disability whereby patients are unable to attend to their own bodily needs without assistance, are bedridden, or require constant nursing attention.

METHODS: Differences in patient characteristics and presenting symptoms were compared between those with and without clinical improvement and favorable outcome. Multivariate logistic regression was used to identify prognostic factors affecting the outcome.

RESULTS: The average age at surgery was 7.2 years, with a male-to-female ratio of 1.2. The average follow-up time was 4 years. At least one of the following symptoms was present in all patients: neurological deficits (83.9%), urological dysfunction (77.4%), or limb deformities (38.7%). After untethering, all patients had either symptoms stabilized (14 patients, 45.2%) or improved (17 patients, 54.8%), and 14 patients (45.2%) achieved total resolving of symptoms. Logistic regression confirmed that younger age (#2 years, odds ratio [OR] 22.0, p5.026), lipomas of filum terminale (OR 25.6, p5.042), and a poor anal tone (OR 10.4, p5.061) were positive prognostic factors for the improvement in symptoms. The functional outcome was determined by the age at surgery (OR 0.9 per year since 1 year old, p5.04) and the presence of limb deformities (OR 0.06, p5.017).

CONCLUSIONS: In conclusion, our study suggests that untethering should be performed immediately once the patient shows evidence of symptomatic lumbosacral cord tethering, irrespective of age. Untethering can interrupt progression of symptoms, but sphincter dysfunction and muscle weakness are more likely to improve or resolve. Benefits can be seen in all patients, but young children (before 2 years old) have a higher chance to gain favorable outcome. Retethering is a main concern during follow-up, particularly for the more complicated lipomyelomeningoceles. Investigations using electrophysiologic and urodynamic studies are helpful for early detection of subtle symptomatic cord tethering or retethering.

Keywords: Lipoma; Lumbosacral; Spina bifida occulta; Tethered cord; Untethering

Mini-review: toward understanding mechanisms of genetic neural tube defects in mice

Harris MJ, Juriloff DM. Mini-review: toward understanding mechanisms of genetic neural tube defects in mice. Teratology. 1999 Nov;60(5):292-305. Review.

We review the data from studies of mouse mutants that lend insight to the mechanisms that lead to neural tube defects (NTDs). Most of the 50 single-gene mutations that cause neural tube defects (NTDs) in mice also cause severe embryonic-lethal syndromes, in which exencephaly is a nonspecific feature. In a few mutants (e.g., Trp53, Macs, Mlp or Sp), other defects may be present, but affected fetuses can survive to birth. Multifactorial genetic causes, as are present in the curly tail stock (15-20% spina bifida), or the SELH/Bc strain (15-20% exencephaly), lead to nonsyndromic NTDs. The mutations indicate that "spina bifida occulta," a dorsal gap in the vertebral arches over an intact neural tube, is usually genetically and developmentally unrelated to exencephaly or "spina bifida" (aperta). Almost all exencephaly or spina bifida aperta of genetic origin is caused by failure of neural fold elevation. The developmental mechanisms in genetic NTDs are considered in terms of distinct rostro-caudal zones along the neural folds that likely differ in mechanism of elevation. Failure of elevation leads to: split face (zone A), exencephaly (zone B), rachischisis (all of zone D), or spina bifida (caudal zone D). The developmental mechanisms leading to these genetic NTDs are heterogeneous, even within one zone. At the tissue level, the mutants show that the mechanism of failure of elevation can involve, e.g., (1) slow growth of adjacent tethered tissue (curly tail), (2) defective forebrain mesenchyme (Cart1 or twist), (3) defective basal lamina in surface ectoderm (Lama5), (4) excessive breadth of floorplate and notochord (Lp), (5) abnormal neuroepithelium (Apob, Sp, Tcfap2a), (6) morphological deformation of neural folds (jmj), (7) abnormal neuroepithelial and neural crest cell gap-junction communication (Gja1), or (8) incomplete compensation for a defective step in the elevation sequence (SELH/Bc). At the biochemical level, mutants suggest involvement of: (1) faulty regulation of apoptosis (Trp53 or p300), (2) premature differentiation (Hes1), (3) disruption of actin function (Macs or Mlp), (4) abnormal telomerase complex (Terc), or (5) faulty pyrimidine synthesis (Sp). The NTD preventative effect of maternal dietary supplementation is also heterogeneous, as demonstrated by: (1) methionine (Axd), (2) folic acid or thymidine (Sp), or (3) inositol (curly tail). The heterogeneity of mechanism of mouse NTDs suggests that human NTDs, including the common nonsyndromic anencephaly or spina bifida, may also reflect a variety of genetically caused defects in developmental mechanisms normally responsible for elevation of the neural folds.

PMID: 10525207

Tethered cord syndrome in children: a review

Bui CJ, Tubbs RS, Oakes WJ. Tethered cord syndrome in children: a review. Neurosurgical Focus. 2007;23(2):1-9.

The treatment of a patient with symptoms of a tethered spinal cord and in whom a fatty infiltrated terminal filum is found is controversial. The authors review their experience and the literature regarding this aspect of occult spinal dysraphism. From experience, transection of a fatty terminal filum in patients with symptoms related to excessive caudal cord tension is a minor procedure that generally yields good results. The most problematic issue in the literature is what patients and symptoms are best suited to surgical treatment.

PMID: 17961017

Tethered cord due to spina bifida occulta presenting in adulthood: a tricenter review of 61 patients

Rajpal S, Tubbs RS, George T, Oakes WJ, Fuchs HE, Hadley MN, Iskandar BJ. Tethered cord due to spina bifida occulta presenting in adulthood: a tricenter review of 61 patients. Journal of Neurosurgery: Spine. 2007 Mar;6(3):210-5.

OBJECT: Children with spina bifida occulta require early surgery to prevent neurological deficits. The treatment of patients with a congenitally tethered cord who present in adulthood remains controversial.

METHODS: The authors studied the medical records of 61 adult patients who underwent surgical untethering for spina bifida occulta at three institutions between 1994 and 2003. Patients who had undergone prior myelomeningocele repair or tethered cord release surgery were excluded. The most common intraoperative findings were lipomyelomeningocele (41%) and a tight terminal filum (36%). The follow-up duration ranged from 10.8 to 149.5 months. Of the 34 patients with back pain, status improved in 65%, worsened in 3%, remained unchanged in 18%, and improved and later recurred in 15%. Lower-extremity pain improved in 16 patients (53%), remained unchanged in 23%, improved and then recurred in 17%, and worsened in 7%. Lower-extremity weakness improved in 47%, remained unchanged in 47%, and improved and then recurred in 5%. Finally, of the 17 patients with lower-extremity sensory changes, status improved in 35%, remained unchanged in 35%, and the information on five patients was unavailable. Surgical complications included three wound infections, one cerebrospinal fluid leak, and two pseudomeningoceles requiring surgical revision. One patient developed acute respiratory distress syndrome and sepsis postoperatively and died several days later.

CONCLUSIONS: Adult-age presentation of a congenital tethered cord is unusual. Despite a slight increase in postoperative neurological injury in adults, surgery has relatively low risk and offers good potential for neurological improvement or stabilization. As they do in children, the authors recommend early surgery in adults with this disorder. The decision to undertake surgery, however, should be modulated by other factors such as a patient's general medical condition and risk posed by anesthesia.

PMID: 17355019

Tethering tracts in spina bifida occulta: revisiting an established nomenclature

Rajpal S, Salamat MS, Tubbs RS, Kelly DR, Oakes WJ, Iskandar BJ.
Tethering tracts in spina bifida occulta: revisiting an established nomenclature.
Journal of Neurosurgery. Spine. 2007 Sep;7(3):315-22.

OBJECT: The goal of the present study goal was to systematically confirm the previously recognized nomenclature for tethering tracts that are part of the spectrum of occult spinal dysraphic lesions.

METHODS: The tethering tract in 20 patients with spina bifida occulta underwent histological examination with H & E staining and epithelial membrane antigen (EMA) immunolabeling, and additional selected specimens were stained with Masson trichrome.

RESULTS: All tethering tracts contained fibrous connective tissue. Four tracts were lined with epithelial cells and either originated within a dermoid cyst, terminated at a skin dimple/sinus opening, or had both of these characteristics. No tethering tracts exhibited EMA positivity or meningeal elements. Although all tethering tracts originated in juxtaposition to the spinal cord, their termination sites were variable.

CONCLUSIONS: Based on histological findings and presumed embryological origin, the authors broadly classified tethering tracts terminating within the dura mater, epidural space, or lamina as "short tethering tracts" (STTs). The STTs occurred mostly in conjunction with split cord malformations and had a purely fibrous composition. Tethering tracts terminating superficial to the overlying lamina were classified as "long tethering tracts" (LTTs), and the authors propose that these are embryologically distinct from STTs. The LTTs were of two varieties: epithelial and nonepithelial, the former being typically associated with a skin dimple or spinal cord (epi)dermoid cyst. In fact, analysis of the data suggested that not every tethering tract terminating in or on the skin should be classified as a dermal sinus tract without histological confirmation, and because no evidence of meningeal tissue-lined tracts was detected, the use of the term "meningocele manqué" may not be appropriate.

PMID: 17877266