Isolated central canal rupture of spinal dermoid

Report of 3 cases

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Spinal dermoid tumors are rare, benign, slow-growing tumors. Rupture of spinal dermoids, in contrast to cranial dermoids, is rarely reported. Rupture in the central canal alone is even more rare, with only a few cases reported in the literature. The presence of fat droplets within the central canal is unusual because the central canal is rudimentary in adults. The authors report 3 such cases and review the pertinent literature.

Abbreviation used in this paper:MRC = Medical Research Council.

Spinal dermoid tumors are rare, benign, slow-growing tumors. Rupture of spinal dermoids, in contrast to cranial dermoids, is rarely reported. Rupture in the central canal alone is even more rare, with only a few cases reported in the literature. The presence of fat droplets within the central canal is unusual because the central canal is rudimentary in adults. The authors report 3 such cases and review the pertinent literature.

Dermoid cysts represent a rare group of tumors manifesting predominantly in adulthood. Rupture is well described in intracranial dermoid tumors. However, rupture of an intraspinal dermoid into the central canal is uncommon and in most cases asymptomatic.4,12 We report 3 unusual cases of lumbar spinal dermoid cysts with asymptomatic rupture and migration of free fat droplets into the central canal.

Case Reports

Case 1

History and Presentation

This 19-year-old male patient, who had undergone surgery for treatment of a lumbosacral meningomyelocele at the age of 3 days, presented to us with complaints of progressive weakness in both lower limbs and urinary incontinence for the preceding 6 years. Neurological examination revealed weakness in his ankles and toes bilaterally (Medical Research Council [MRC] Grade 0/5) with 75% sensory loss in the L4–S1 dermatomes on the both sides. Magnetic resonance imaging of the lumbosacral region demonstrated an intramedullary lesion of heterogeneous signal intensity at the L2–3 level with foci of hyperintensity within the dilated central canal up to the T-10 level on T1-weighted images, suggestive of a dermoid cyst with fatty dissemination in the central canal (Fig. 1). The lumbar subarachnoid space was free of fatty droplets.

Fig. 1.
Fig. 1.

Case 1. A: Sagittal T1-weighted MR image showing an intramedullary lesion with heterogeneous signal intensity at the L2–3 level with hyperintense signal within the cord extending up to the T-10 level. B and C: Axial T1-weighted images with (C) and without (B) fat saturation. The hyperintense signal that is evident in the center of the cord (white arrow) in B is suppressed on the fat-saturation image (white arrow, C), suggestive of fat in the dilated central canal.

Operation and Postoperative Course

The patient underwent L2–4 laminectomy and excision of the dermoid. The surgery included laminectomy and opening of the dura. Myelotomy was done at the point where the cord tissue was thinnest. The contents of the dermoid cyst, which included yellowish-white pultaceous material mixed with hairs, were removed. This was followed by removal of the cyst wall/capsule, which was adherent to the cord tissue but could nevertheless be excised completely. The patient's condition remained stable after the operation, with no change in motor power. As of the most recent follow-up, 4 months after surgery, he was doing well with no new-onset deficits.

Case 2

History and Presentation

This 23-year-old man presented with a 5-year history of pain in his lower back and a 6-month history of urinary and bowel incontinence. There was no history of trauma. Examination demonstrated normal strength in both lower limbs except for the left extensor hallucis longus, which was weak (MRC Grade 4/5). The patient also had an associated decrease in anal sphincter tone. Magnetic resonance imaging of the lumbosacral region demonstrated an intramedullary lesion of heterogeneous signal intensity at L1–2 with foci of hyperintensity up to the T-12 level, supporting a diagnosis of conus medullaris dermoid with intracanalicular rupture (Fig. 2).

Fig. 2.
Fig. 2.

Case 2, preoperative MRI. A: Sagittal T1-weighted MR image showing an intramedullary lesion with heterogeneous signal intensity at the L1–2 level with hyperintense signal intensity in the cord extending up to the T-12 level. B: Coronal T1-weighted MR image showing a heterogeneous signal intensity lesion with extension of the hyperintensity above the lesion. C: Axial T1-weighted MR image showing signal hyperintensity in the dilated central canal.

Operation and Postoperative Course

Laminectomy was performed, and the dermoid cyst was excised using the same surgical techniques as described in Case 1. The contents of the dermoid were completely evacuated, and most of the cyst wall was excised; the cyst wall could not be completely excised, as it was badly adherent to the cord. The patient's condition remained stable after the operation. At the 10-month follow-up, he reported improvement in back pain and urinary incontinence. Follow-up MRI (10 months after surgery) revealed no residual dermoid but persistent fat droplets in the central canal (Fig. 3).

Fig. 3.
Fig. 3.

Case 2, postoperative MRI. A: Sagittal T1-weighted MR image showing hyperintense signal at T-12 and no residual lesion at L1–2. B: Axial T1-weighted image showing hyperintense signal in the dilated central canal (arrow). C and D: Sagittal T2-weighted images showing a heterogeneous signal intensity lesion at T-12, with suppression of the hyperintense component on fat saturation imaging (D) suggestive of fat in the dilated central canal.

Case 3

History and Presentation

This 31-year-old man presented with low-back pain and sensory disturbance over the lateral aspect of his right foot of 7 years' duration. He did not have any bowel or bladder symptoms. Neurological examination revealed normal strength in both lower limbs, with a 50% sensory loss in the right S-1 distribution. Magnetic resonance imaging revealed a conus lesion that was heterogeneously hyperintense on both T1- and T2-weighted images. On T1-weighted images signal hypersensitivity within the dilated central spinal canal extending craniad to the C-6 level (Fig. 4). A diagnosis of conus dermoid with rupture into the central canal was made, and resection of the dermoid was planned.

Fig. 4.
Fig. 4.

Case 3. Sagittal T1-weighted MR images showing a heterogeneous signal intensity lesion in the conus with hyperintense fat droplets within the dilated central spinal canal extending up to the C-6 level.

Operation and Postoperative Course

The patient underwent laminectomy and excision of the dermoid. The contents of the cyst were removed completely; however, some parts of the cyst wall were badly adherent to the cord and hence were left behind. Histological examination confirmed the diagnosis of dermoid cyst. At the 8-month follow-up, the patient's neurological condition was the same as in the preoperative period.

Literature Review

A systematic PubMed search of the MEDLINE database was performed to identify case reports or series involving spinal dermoids that ruptured into the central canal using the key words “spinal dermoid,” “ruptured,” and “central canal.” Searches were restricted to articles published in the English language during or before December 2012. The reference lists of these reports were also searched. A total of 7 articles were found.

Review of the literature revealed that the age of the patients at the time of presentation ranged from 19 to 55 years. The duration of symptoms ranged from 5 months to 8 years. Associated spinal dysraphism was seen in one patient. All the patients had fat droplets in the central canal, and 2 patients also had fat droplets in the subarachnoid space. Fat droplets extended craniad in all cases—with the upper level of extension ranging from T-10 to the cervicomedullary junction.

Discussion

Spinal dermoid cysts are benign neoplasms composed of keratinized squamous epithelium covered by connective tissue with islands of dermis containing hair follicles and sebaceous glands. They have been proposed to arise from the inclusion of ectopic embryonic rests of the ectoderm and mesoderm in the spinal canal at the time of neural tube closure between 3 and 5 weeks of fetal life.4,13 However, sometimes dermoids can also arise iatrogenically, after the introduction of dermal elements into the subarachnoid space by procedures like lumbar puncture, spinal surgery, or trauma.4,11 They can also be associated with overlying bony malformations, myelomeningocele, split cord malformation, hypertrichosis, and/or a dermal sinus tract.14 In our series, the first patient had a spinal dermoid in association with spinal dysraphism.

Spinal dermoid cysts can be intramedullary, intradural-extramedullary, or extradural. Dermoids have been reported to constitute 0.7%–1.8% of tumors of the central nervous system and 1%–10% of intraspinal tumors.1,3,15 The lumbosacral region is the most commonly affected, with lesions involving the cauda equina and/or conus medullaris in about 60% of cases. The upper thoracic (10%) and cervical regions (5%) are less frequently involved. 8

There is a slight male predominance, and most cases are diagnosed during the 2nd and 3rd decades of life. Although present from birth, dermoids usually manifest in adulthood and generally grow slowly, which may explain the relative paucity of symptoms. Patients may occasionally become acutely symptomatic following rupture of the cystic lesion, which may elicit an inflammatory meningeal reaction. Dermoids may also be complicated by infection or very rarely by malignant degeneration.10

Dermoids are typically unilocular cystic lesions with viscous contents ranging in color from pale yellow to brown. The cyst wall is made of up of thick connective tissue lined by stratified squamous epithelium and may contain dermal components such as hair or sebaceous or sweat glands.2 The wall may occasionally be calcified, and bone and cartilage may even be found within the lesion itself. Dermoid tumors may show two distinct parts, a solid and fluid one; the fluid part may give rise to fluid level on imaging studies.8

With the advent of MRI, early diagnosis of dermoids is now possible, and the number of reported dermoid tumors is increasing. They are commonly visualized as heterogeneous lesions with very high signal intensity on T1-weighted images and low signal intensity on T2-weighted images, due to their lipid content.9 Magnetic resonance imaging can also demonstrate fat droplets spreading into the subarachnoid space or, quite rarely, into the central spinal canal due to rupture of the cyst; these fat droplets appear as areas of signal hyperintensity on T1-weighted images. The cystic portions of dermoids does not usually show contrast enhancement, as they lack vascularity. The solid portion of the tumor and the tumor capsule usually show contrast enhancement.

Rupture of intracranial dermoids has been well documented in the literature and is frequently symptomatic. The free fat droplets can cause chemical meningitis, vasospasm, or rapidly developing hydrocephalus. Clinical symptoms of acute rupture are headache, nausea, vomiting, vertigo, vision problems, aseptic chemical meningitis, hemiplegia, mental changes, and coma.3,15 The fat droplets in the subarachnoid and ventricular spaces may lead to arachnoiditis and subsequently to ventriculitis. With the frequent use of MRI it has been found that spontaneous dermoid rupture, which was previously thought of as a rather serious or fatal condition, is quite common and usually only slightly symptomatic or asymptomatic.

Unlike spontaneous rupture of cranial dermoids, spontaneous rupture of spinal dermoids is a rare event, and only a few cases have been reported in literature.3–5,7,16 In most of these cases, fat droplets were seen in the intracranial cisterns and ventricles, or in the spinal subarachnoid space. Fat droplets within the central canal are even more rare because the central canal is rudimentary in adults.3–6,12 The cases of rupture of dermoids into the central canal that have been described in the literature are summarized in Table 1. Rupture and subsequent release of fatty contents into central canal is usually asymptomatic or would only cause mild and nonspecific symptoms, unlike rupture of cranial dermoids, which is associated with an acute presentation. None of our patients had an acute presentation, and in all 3 cases the rupture was detected on imaging studies. The patient in Case 3 in our series did not have symptoms pertaining to intraspinal spread despite of dissemination up to the C-6 level. Symptoms might be expected to occur upon migration of fat droplets into the intracranial cisterns and ventricles. Barsi et al. described craniad spread of ruptured lumbar dermoid contents via a dilated central canal to the intracranial cisterns and ventricles.3 Garg et al. proposed that hydromyelia secondary to tumor and specific tumor morphology might facilitate the selective rupture of dermoids into the central canal, and its presence in a case of spinal dermoid should raise the possibility of rupture into the central canal, and if indicated, a screening study of the spine and brain should be done.6

TABLE 1:

Summary of reported cases of isolated rupture of spinal dermoids into the central canal*

Authors & YearPt Age (yrs), SexSigns & SxDuration of SxRadiological FindingsLocation of Fat DropletsLevel of Extension of Fat Droplets
Barsi et al., 199227, Mparaparesis, urinary difficulties, sensory disturbances from the level of L-1, increasing distallyNRheterogeneous signal intensity from mid–T-11 to mid–L-1subarach space & central canalup to C-5
Calabrò et al., 200033, Mparaparesis, sensory disturbances2 yrsintraspinal mass at L-1, heterogeneously hyperintense on T-1 & hypointense on T-2central canalup to C-6
Karadag et al., 200255, Mleft leg pain & weakness, sensory disturbance8 yrsheterogeneously hyperintense intramed mass at T-12 & L-1subarach space & central canalcervical & thoracic
Garg et al., 200332, Mpain, mild weakness of left ankle dorsiflexion & plantar flexion, absent left ankle jerk, 20% loss of sensation in left L-5 distribution4 yrsintramed lesion w/ heterogeneous signal intensity at the conuscentral canalT-10
34, Mlow-back pain, radiating pain along both lower limbs, premature ejaculation, bowel incont, right EHL weakness, decrease in anal sphincter tone7 mosheterogeneous mass at conus w/ syrinx extending up to T-9 levelcentral canalT-10
Goyal et al., 200432, Mback pain, weakness of both lower limbs, bladder dysfunction5 mosheterogeneous mass at conus w/ syrinx extending up to T-9 levelcentral canalcervicomedullary jx
Kasliwal et al., 200726, Mdysesthetic pain in right chest, patchy sensory loss in right T4–8 dermatomes1 yrlesion in conuscentral canalwhole spine
Vyas et al., 201035, Mnumbness & weakness of all 4 limbs, bladder & bowel incont, absence of deep tendon reflexes in lower limbs, absence of bulbocavernosus reflex4 yrsheterogeneous dermoid at conuscentral canalcervicomedullary jx & 4th ventricle
present series19, Msurgically treated lumbosacral meningomyelocele, weakness of both lower limbs, bladder incont, sensory disturbances6 yrssplit cord malformation at L4–5 w/ subcutaneous lipoma & dermoid at L3–4 w/ heterogeneous signal intensitycentral canalT-10
23, Mlow-back pain, bowel & bladder incont, left EHL weakness5 yrsheterogeneous mass at conuscentral canalT-11
31, Mlow-back pain, sensory disturbances7 yrsintramed lesion w/ heterogeneous signal intensity at conuscentral canalC-5

EHL = extensor hallucis longus; incont = incontinence; intramed = intramedullary; jx = junction; NR = not reported; Pt = patient; subarach = subarachnoid; Sx = symptoms.

One of our patients had associated spinal dysraphism operated at 3 days of life while the other two did not have any other associated anomalies. All of them had fat droplets in the central canal. The third patient in our series had a small primary lesion at the conus, with extensive dissemination in the cervicothoracic central canal reaching up to C-6 level. Surprisingly, however, he did not seem to have any symptoms resulting from the dissemination. Such extensive spread might have been caused by an associated syringomyelia.

Karadag et al. reported a case of a ruptured conus dermoid with fat droplets in the subarachnoid space as well as in the dilated central spinal canal.11 They concluded that MRI is the modality of choice for the diagnosis of dermoid tumors and is also quite reliable in the evaluation of the presence of rupture and its extent in the subarachnoid space or, rarely, the central spinal canal.

Management of the ruptured dermoid cyst in the central canal consists of the excision of the primary lesion only. No intervention is required for the migrated fat droplets in the central canal. However, such cases need close follow-up, as migration of fat droplets into the subarachnoid spaces and ventricles might lead to meningitis and hydrocephalus.

Only one of our 3 patients showed improvement in the postoperative period. Postoperative outcome has not been described in most of the cases reported in the literature. Only one patient has been previously reported to improve following surgery.6

Postoperative MRI was available in only one of our cases, and it revealed the persistence of the fat droplets in the central canal, even 10 months after surgery. None of the other reported cases include postoperative MRI findings. The finding of persistent fat droplets in our case suggests that the fat droplets in the central canal resulting from the rupture of a spinal dermoid may persist for long time, again emphasizing the need for close follow-up of these patients. The long-term outcome and effects of this rare phenomenon are not yet clear due to the lack of long-term follow-up in our cases as well as those previously reported in the literature.

Conclusions

Rupture of a spinal dermoid into the central canal is very rare, with most affected patients being asymptomatic. MRI is the investigation of choice to diagnose the condition and to determine the extent of distribution of ruptured content into the central canal and subarachnoid space. Cases should be managed with surgical excision of the primary lesion followed by close observation.

Disclosure

The authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this paper.

Author contributions to the study and manuscript preparation include the following. Conception and design: both authors. Acquisition of data: both authors. Analysis and interpretation of data: Garg. Drafting the article: Garg. Critically revising the article: both authors. Reviewed submitted version of manuscript: both authors. Approved the final version of the manuscript on behalf of both authors: Kumar. Statistical analysis: both authors. Administrative/technical/material support: both authors. Study supervision: Kumar.

This article contains some figures that are displayed in color online line but in black-and-white in the print edition.

References

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Article Information

Address correspondence to: Rajinder Kumar, M.B.B.S., Rm. No. 605, Cardio-Neuro Centre, All India Institute of Medical Sciences, New Delhi 110029, India. email: rklaythalling@rediffmail.com.

Please include this information when citing this paper: published online June 13, 2014; DOI: 10.3171/2014.5.SPINE13900.

© AANS, except where prohibited by US copyright law.

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Figures

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    Case 1. A: Sagittal T1-weighted MR image showing an intramedullary lesion with heterogeneous signal intensity at the L2–3 level with hyperintense signal within the cord extending up to the T-10 level. B and C: Axial T1-weighted images with (C) and without (B) fat saturation. The hyperintense signal that is evident in the center of the cord (white arrow) in B is suppressed on the fat-saturation image (white arrow, C), suggestive of fat in the dilated central canal.

  • View in gallery

    Case 2, preoperative MRI. A: Sagittal T1-weighted MR image showing an intramedullary lesion with heterogeneous signal intensity at the L1–2 level with hyperintense signal intensity in the cord extending up to the T-12 level. B: Coronal T1-weighted MR image showing a heterogeneous signal intensity lesion with extension of the hyperintensity above the lesion. C: Axial T1-weighted MR image showing signal hyperintensity in the dilated central canal.

  • View in gallery

    Case 2, postoperative MRI. A: Sagittal T1-weighted MR image showing hyperintense signal at T-12 and no residual lesion at L1–2. B: Axial T1-weighted image showing hyperintense signal in the dilated central canal (arrow). C and D: Sagittal T2-weighted images showing a heterogeneous signal intensity lesion at T-12, with suppression of the hyperintense component on fat saturation imaging (D) suggestive of fat in the dilated central canal.

  • View in gallery

    Case 3. Sagittal T1-weighted MR images showing a heterogeneous signal intensity lesion in the conus with hyperintense fat droplets within the dilated central spinal canal extending up to the C-6 level.

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