ab c d e Case Study 1 A 9-month-old male child was brought for consultation because of a “tail-like” structure in the low back since birth. Examination revealed a subtle thinning of the right lower extremity and a caudal appendage (pseudotail) in the lower lumbosacral region ( a). Plain radiographs revealed spina bifida at L5. MRI revealed a tethered cord with fatty filum termi- nale. The pseudotail is a short, stump-like structure ( b). Spinal dysraphism is the most frequent coexisting anomaly in both anatomical variants (50%). Other associated lesions include tethered cord syndrome, lipomas, teratomas and glio- mas. Investigation of children born with human tail appendages should include a thorough neurological examination, plain X-ray films of the lumbosacral region and contrast MRI to look for dysraphism and associated lesions. During sur- gery, a fibrous, fatty filum terminale was seen extending from the base of the appendage through the defect in the bone and dura. The hypertrophied and fat-infiltrated filum ended at the tip of the low lying conus ( c). The filum is coagulated with bipolar coagulation as there is typically a small vein within the filum ( d). We prefer to remove a segment of the affected filum ( e) and submit it to pathological examination for confirmation. After surgery, there was no change in the neurological status of the patient. and are found in patients with caudal agenesis [32]. They are usually discovered in older children or adults complaining of low back pain, urinary incontinence or constipation. Myelocystocele A myelocystocele represents a cystic dilatation of the spinal cord in the cervical or lumbar spine A myelocystocele consists of a cystic dilatation of the lower end of the spinal cord or the cervical region enclosed in a skin covered back mass [5, 39]. The spinal cord is low lying and tethered [5]. The subcutaneous fat lines the cyst but does not extend into the sac or the cord. Malformations of the Spinal Cord Chapter 29 805 The inner terminal cyst communicates with the central canal of the spinal cord, whereas the outer dural sac communicates with the subarachnoid space. The outer and inner fluid spaces usually do not communicate. Tethering results from the attachment of the myelocystocele to the inferior aspect of the spinal cord. The syringocele lies caudal to the meningocele in all cases and bulges through a wide spina bifida, producing a skin-covered subcutaneous mass that may be huge. Patients with terminal myelocystoceles typically have no bowel or bladder con- trol and poor lower-extremity function [32]. Lipomyelomeningocele/Lipomyeloschisis In lipomyeloschisis and lipomyelomeningocele, the intraspinal lipoma is a por- tion of a larger subcutaneous lipoma, extending into the spinal canal through a wide posterior spina bifida and tethering the spinal cord; it consists of a skin-cov- ered back mass that contains neural tissue, CSF and meninges [5, 39]. The bony anomalies include a large defect in the posterior elements of the spine, segmenta- tion anomalies and sacral dysgenesis. Association with Chiari I malformation may be seen [5]. In lipomyelomeningoceles, a subcutaneous lumbosacral mass is found in 90% of patients [48]. Additional skin abnormalities are found in 50% of patients and may include an area of hypertrichosis, a capillary hemangioma, a dermal sinus tract, a dimple, or an additional appendage. Because the mass is clinically evident at birth, the diagnosis is usually obtained before neurological deterioration ensues [5]. Differentiation between lipomyeloschisis and lipomyelomeningocele is based on whether the placode-lipoma interface lies within the anatomic boundary of the spinal canal or outside (i.e. within an meningeal outpouching). A further classification widely used by neurosurgeons divides these lipomas into three sub- categories: dorsal, transitional, and caudal, depending on whether the placode is segmental, parietal, or terminal [26]. Spinal Lipoma (Intradural and/or Intramedullary) Differentiation of the different entities is crucial Intradural and intramedullary lipomas are similar to lipomas with dural defects. However, they are contained within an intact dural sac. In other words, they are localized within the intradural space [1, 5, 26, 32, 39]. Failure to differentiate between lipomyelomeningoceles, intradural lipomas and filum terminale lipo- mas may lead to inaccurate assumptions regarding prognosis [4]. These lesions have different clinical presentations, courses and outcomes [4]. Intradural lipomas account for 24.1% of all spinal lipomas [39]. The cord is low lying and tethered to the lipomatous tissue [5]. Intradural lipo- mas are commonly located at the lumbosacral level, but may be found anywhere in the spinal canal, which may be focally or diffusely expanded depending on the size of the mass ( Fig. 1). Spinal lipomas can be associated with diastematomyelia The lipoma may be associated with other cord anomalies such as diastemato- myelia. Associated vertebral anomalies consisting of spina bifida at one or sev- eral vertebral levels may be present [5]. Lipomas located at the bottom of the the- cal sac usually present clinically with tethered cord syndrome, whereas cervico- thoracic lipomas generally produce insidious signs of spinal cord compression. It is widely accepted that congenital intraspinal lipomas are anatomically stable lesions. However, the subcutaneous and intraspinal components may grow as part of the normal increase of adipose tissue that occurs throughout childhood, other than in particular conditions such as obesity or pregnancy [48]; therefore, clinical worsening may ensue if the lesion is left untreated. 806 Section Spinal Deformities and Malformations ab Figure 1. Intradural spinal lipoma MRI of intradural spinal lipoma in a 37-year-old man. a Sagittal T1W image shows the spinal cord tethered to the anterior surface of an intradural lipoma. b Axial images show indistinct fat-cord interface. Anterior Sacral/Lateral Thoracic Meningocele Anterior sacral meningocele occurs when there is communication between the retroperitoneal or infraperitoneal space and spinal subarachnoidal space throughadefectintheanteriorsacrum.Themassthatdevelopsisafibrouscon- nective tissue capsule filled with spinal fluid, and may contain some sacral nerve root elements. This malformation is three times more common in females. Simi- lar abnormalities may occur at the lumbosacral and thoracic levels. Tight Filum Terminale/Filum Terminale Lipoma The filum terminale is a viscoelastic formation usually <2.0 mm wide [40], which allows the conus to ascend during flexion of the spine. The tight filum ter- minale (9% of all closed spinal dysraphisms) is characterized by a short, hyper- trophic, fatty filum terminale that produces tethering of the spinal cord and Malformations of the Spinal Cord Chapter 29 807 a b Figure 2. Fatty filum terminale Fatty filum terminale in a 35-year-old woman with tethered cord syn- drome. a, b Sagittal and axial T1-weighted images show that the filum terminale is largely replaced by fat and moved dorsally. The spinal cord is tethered and low. impaired ascent of the conus medullaris [32]. A filum terminale greater than 2 mm in diameter refers to the thick-tight filum terminale [5, 19, 48]. The thickening is caused by lipomatous or fibrous tissue. The occurrence of incidental fat within the terminal filum in a normal adult population has been estimated to be 3.7% in cadaveric studies [48]. Radiologically, the conus is either normal in location or low-lying with a thickened filum terminale [5]. In 86% of patients, the tip of the conus medullaris lies inferior to L2 [19, 32]. This anomaly may be difficult to diagnose, although the association of clinical and A filum terminale of > 2 mm is defined as a fibrolipoma neurological features may lead one to suspect it. The filum terminale must not be >2 mm in diameter and no fatty tissue must be present; otherwise, the abnormality is best defined as a filar lipoma or fibrolipoma [39]. The terminal filum is the tethering agent, and these patients respond to sectioning of the filum ( Fig. 2 ). In the majority of patients, there are no cutaneous anomalies, but posterior spina bifida, scoliosis, and kyphoscoliosis are associated in a high percentage of cases. Dermal Sinus, Fistula, Dermoid/Epidermoid Tumors The dermal sinus is an epithelium-lined fistula that extends inward from the skin surface and can connect with the central nervous system and the meninges coating, thereby causing tethering [5, 48]. It is found more fre- quently in the lumbosacral region, although cervical, thoracic, and occipital locations are possible [32, 39]. Although the cutaneous abnormality is usually evident at birth, some patients are not referred to medical attention until they develop complications such as local infection or meningitis and abscesses that may result from bacteria invading the CNS through the dermal sinus tract [48]. 808 Section Spinal Deformities and Malformations They also may connect to a hypertrophic or fibrolipomatous filum terminale, as well as to a low-lying conus medullaris or intraspinal lipoma. In a considerable percentage of cases, dermal sinuses are associated with dermoid and epidermoid tumors, generally located at the level of the cauda equina or near the conus medullaris [5, 13, 32]. This association was found in 11.3% of cases [32]. Neuroenteric/Bronchogenic Cysts and Fistula (Split Notochord Syndrome) There is abnormal splitting of the notochord with persistent connection between the gut and the dorsal skin [5, 19, 22]. The abnormal communication may involve esophagus, bronchus, and intestines. The abnormal tract may become obliterated at any point with consequent variable outcome such as a cyst (neuroenteric cyst, bronchogenic cyst), diverticulum or fistula [5, 32]. These cysts are lined with a mucin secreting epithelium that resembles the alimentary or bronchogenic epi- thelium. Whereas the cyst is frequently associated with anterior or posterior spina bifida, it may be found without any associated dysraphic anomalies [48]. Split Cord Malformations (Diastematomyelia, Diplomyelia) Split cord malformation (SCM) is a form of occult spinal dysraphism that also produces spinal cord tethering [5, 42]. Split cord malformations are classically defined as diastematomyelia. Two forms of split cord malformation have been described. From a strict point of view, diastematomyelia refers to cord splitting and diplomyelia to cord duplication [26, 34, 39]. Split cord malformations are commonly located in the lumbar and thoracic spine Split cord malformations are usually located in the lumbar and thoracic regions and are more common in girls [5, 42]. Type I split cord malformation accounts for 40–50 % of all SCMs. There is a double dural sac, a double spinal canal and two hemicords separated by an extradural bony spur [26, 34, 39]. Type II split cord malformation accounts for 50– 60% of all SCMs. There is one dural sac, one spinal canal, and two equal hemicords between which there may be an anterior-posterior, fibrous intradural spur [26, 34, 39, 48]. Klippel-Feil syndrome (ranging from congenital fusion of only the vertebral bodies to entire fusion of the vertebrae and can be associated withhemivertebrae and spilt posterior elements) is known to have a potential association with split cord malformations [42] ( Fig. 3). Caudal Regression/Agenesis Caudal regression syndrome is a heterogeneous constellation of caudal anomalies comprising total or partial agenesis of the spinal column [5, 39], anal imperfora- tion, genital anomalies, bilateral renal dysplasia or aplasia, and pulmonary hypo- plasia. The lower limbs usually are dysplastic and show distal leg atrophy and a short intergluteal cleft. Agenesis of the sacrococcygeal spine may be part of syndro- mic complexes such as OEIS (omphalocele, cloacal exstrophy, imperforate anus, and spinal deformities), VACTERL (vertebral abnormality, anal imperforation, tra- cheoesophageal fistula, renal abnormalities, limb deformities), and the Currarino triad (partial sacral agenesis, anorectal malformation, and presacral mass: tera- toma and/or meningocele) [19] ( Fig. 4 ). Lipomyelomeningocele and terminal mye- locystocele are associated in 20% of cases. There is a definite association with maternal diabetes mellitus (1% of offspring of diabetic mothers) [19]. It is believed that hyperglycemia occurring early during gestation could influence further devel- opment of Hensen’s node and the tail bud in genetically predisposed embryos. Malformations of the Spinal Cord Chapter 29 809 ab c d e Figure 3. Split cord malformation Thoracal Type I split cord malformation in a 50-year-old man with tethered cord syndrome. a Sagittal bony spur is visible. b T2-weighted image shows bony spur projecting into spinal canal. Vertebral segmentation pathology of T5–7 is also visible. c Coronal T1-weighted image shows the midline bony spur and split cord. d Axial CT presented bony spur. e Axial MRI shows nicely dural dual sacs and intervening bony spur. 810 Section Spinal Deformities and Malformations a b Figure 4. Caudal regression syndrome Two patients (10-month-old and 9-day-old) with Currarino triad. Both have caudal regression syndrome Type II (lesser degree of sacrococcygeal agenesis). In case a the spinal cord is tethered to a sacral lipoma and epidermoid, in case b to a malformative tumor. There are two types of caudal regression abnormality depending on the position of the conus medullaris [22, 26, 39]: Type I: If the derangement is severe (spine ending at S2 or above), then not onlythecaudalcellmassbutalsopartofthetruenotochordfailstodevelop. Type II: With a minor degree of dysgenesis (S3 or lower levels present), only thewhole,orapart,ofthecaudalcellmassfailstodevelop. Neuroectodermal Appendages Neuroectodermal appendages are tail-like appendages arising in the posterior midline that have sinus tracts extending into the neural canal. It has been pro- posed that these develop initially as dermal sinus tracts with continued epitheli- alization outward to form an appendage ( Case Study 1). Classification of Tethered Spinal Cord Tethered cord syndrome may even occur with the conus at L1/2 Spinal cord anomalies can also be presented based on the conceptual framework of a tethered cord because of their association with spinal malformations and the implications for treatment. The original description of spinal cord tethering in association with a thickened filum terminale was offered by Garceau (1953). The term tethered spinal cord was coined by Hoffman et al. (1976) [9]. Classically tethered cord is defined as having the tip of conus below the L2 disc space and pathologically elongated spinal cord. However, in the medical literature, there are many publications of tethered cord syndrome with the conus in a normal position [37, 40, 46, 48]. Tethered cord canbedifferentiatedintotwogroups( Table 5): primary tethered cord secondary tethered cord Malformations of the Spinal Cord Chapter 29 811 Table 5. Classification of tethered cord Primary tethered cord Secondary tethered cord spinal cord malformations with back mass postsurgical spinal cord malformations (retethering by scar, dermoid, arachnoid, cysts) spinal cord malformations without back mass postsurgical intradural operations (tumors, infections) The term primary tethered cord has been used by Sarwar et al. [33] with regard to associated spinal malformations. Secondary tethered cord applies to scarring of the spinal cord or within the spinal canal due to previous myelomeningocele/ meningocele repair [8, 10] and other intradural spinal operations such as spinal cord tumors [35, 58]. When closed spinal dysraphism becomes symptomatic they present as a tethered cord syndrome. Clinical Presentation History Open spinal dysraphism is discovered at birth because of the back mass and pri- mary associated conditions (cutaneous markers, neurological deficits and ortho- pedic deformities). But a significant number of patients with closed spinal dysra- Tethered cord can remain undiagnosed until a late age phism may reach adulthood with their disease undiagnosed. Some cases are dis- covered even as late as 72 years of age [17, 57, 58]. Often, adult patients with teth- ered cord syndrome are misdiagnosed as having a “failed back syndrome” [58]. These patients present for medical assessment because of: development of new symptoms progression of previously established neurological deficits orthopedic deformities acute neurological deterioration after mechanical stresses Tethered Cord Syndrome The prevailing clinical symptoms in closed spinal dysraphism are those of a teth- ered cord syndrome [12, 30, 53, 58]. This syndrome is a functional disorder which is almost universally associated with spinal dysraphism [5, 19], such as lipomyelo- meningocele, split cord malformation, dermal sinus as well as previously oper- ated on myelomeningoceles, which tether the spinal cord within the spinal canal and result in excessive tension of spinal cord. It is associated with a progressive neurological, orthopedic and urologic deterioration that results from spinal cord tethering due to various dysraphic spinal abnormalities [19, 43, 58]. Yamada et al. introduced the term tethered cord syndrome for patients suffering from a teth- ered cord. In the neurosurgical literature, McLone and Pang and Yamada popular- ized this entity [48, 58, 59, 60]. In 1982, Pang and Wilberger showed that tethered cord syndrome exists not only in children but also in adults [2, 25, 60]. The late onset symptomatic presentation is related to cumulative effects of repeated stretching-microtrauma during flexion and extension [48]. Tethered cord syndrome can become symptomatic quite subtly and be slowly progressive, but can also result from sudden stretching of the mechanically fixed spinal cord at any age [9, 19]. Some precipitating events have been reported in the literature as follows [12, 30, 36, 48]: Precipitating events can make tethered cord symptomatic heavy lifting bending movements 812 Section Spinal Deformities and Malformations traumatic injury sudden movements lithotomy position sexual intercourse childbirth sport activities Consider the possibility of a low conus before a lumbar puncture There are also various reports in the literature of spinal neuronal damage, follow- ing spinal anesthesia, with patients who have previously undiagnosed tethered cord with a low lying conus [49, 62]. The cardinal sy mptom of tethered cord is: The cardinal symptom of tethered cord is pain pain. The pain is usually located in the lower back [30]. The pain is increased with activity and relieved by rest. Yamada et al. described three postural changes (postural pain triade) that typically worsen pain in tethered cord syndrome patients [15]. They called these signs the “three Bs” [15, 58]: the inability to sit with legs crossed like buddha difficulty with slight bending at the waist inability to hold a baby or light material at the waist level while standing Additional findings are: low back pain and leg pain anorectal and perineal pain fatigue recurrent bladder infections progressive leg weakness patchy sensory loss sacral sensory loss gait disturbance bladder and bowel dysfunction (incontinence) sexual dysfunction progressive deformity (scoliosis, foot and leg deformities) Physical F indings Regardless of the etiology of the primary tethering, children present to special- ists with one or more of its typical abnormalities. In newborns and infants, the diagnosisoftetheredcordsyndromeisoftenconfusedwithcerebralpalsy[36]. Cutaneous Markers Midline cutaneous abnormality may indicate tethered cord Most patients with a tethered cord have a mark of discoloration or lesion of some type on their skin in the midline [14, 19, 35, 48]. These skin markers are mostly localized in the lumbosacral area and are present in 50–60% of patients who pre- sent with tethered cord syndrome [2, 7, 19, 32, 35, 48]. Most common findings in decreasing frequency are: myelomeningocele sac over the back subcutaneous lipoma deviation of the gluteal furrow hypertrichosis cutaneous hemangioma, port-wine stain dermal sinus, dimple skin tag-tail (caudal appendages) pigmentary nevus Malformations of the Spinal Cord Chapter 29 813 A midline dimple or pinpoint ostium can indicate a dermal sinus A midline dimple or pinpoint ostium can indicate a dermal sinus. It is often found in association with hairy nevus, capillary hemangioma, or hyperpig- mented patches. The cutaneous opening of a dermal sinus tract differs from that of a sacrococcygeal fistula [5, 39]. While dermal sinus tracts are found above the natal cleft and are usually directed superiorly, sacrococcygeal pits are found within the natal cleft with a tract extending either straight down or infe- riorly. Neurological Presentation Individual patients often have more than one symptom or sign. However, one of the clinical features is usually predominant over the other [14, 19, 35, 48, 50]. Most common findings in decreasing frequency are: weakness of the lower limbs reflex changes muscle atrophy muscle spasticity and contractures patchy sensory loss sphincter (bowel, bladder) dysfunction trophic painless ulcers Or thopedic Deformities Examine shoes for signs of wear Various orthopedic deformities are common in spinal dysraphism patients. Often more than one deformity is seen in a single patient [14, 19, 48]. Approxi- mately 75% of patients with tethered cord present with orthopedic anomalies [48]. Most common findings in decreasing frequency are: scoliosis kyphosis, exaggerated lordosis lower limb length discrepancy foot deformities (equinovarus, pes cavus, pes planus) hip subluxations Asymmetric foot size may be an indicator of tethered cord Asymmetric foot size may also be an indicator for a tethered cord. It is also important to examine the worn shoes of patients to look for wearing out of the tips and soles of the shoes [36]. Diagnostic Work-up Prenatal Diagnosis Serum maternal -fetoprotein examination and ultrasonography can identify a large number of these afflicted fetuses with myelomeningoceles between 16 and 20 weeks gestation [20, 24, 28]. Many parents then make the decision to interrupt the pregnancy, which probably is why there has been a significant decrease in the number of those born with this anomaly in western countries. Dietary supple- mentation with folic acid via the mother prior to and during pregnancy is protec- tive and has contributed to the decreased incidence of this disease [39]. Ultrasonography An ultrasound examination is recommended for women at-risk (positive serum -fetoprotein screening, previously affected child, maternal drug intake associ- ated with spinal malformations in the fetus). Ultrasound can detect spina bifida 814 Section Spinal Deformities and Malformations . signs of spinal cord compression. It is widely accepted that congenital intraspinal lipomas are anatomically stable lesions. However, the subcutaneous and intraspinal components may grow as part of. spinal cord within the spinal canal and result in excessive tension of spinal cord. It is associated with a progressive neurological, orthopedic and urologic deterioration that results from spinal. myelocystocele consists of a cystic dilatation of the lower end of the spinal cord or the cervical region enclosed in a skin covered back mass [5, 39]. The spinal cord is low lying and tethered [5].