Infected cervico-dorsal dermoid cyst with fluid - fluid level.

We report a case of a 22-year-old female who was operated at the age of 3 months for cervico-dorsal swelling. She presented with gradual onset, progressively worsening dull aching pain in the cervico-dorsal region, 21 years following previous surgery. Magnetic resonance imaging showed intradural dermoid cyst with the fluid level. She underwent excision of the dermoid cyst with excision of the wall. The clinical profile, etiopathogenesis, radiological features, and management of intraspinal dermoid cysts are discussed in the light of current literature.

Introduction

Dermoid cysts constitute 1.4–6% of the spinal tumors.[1234] Infected dermoid cysts are further rare and should be suspected in patients who have a contributory history such as trauma or surgery. We report a case of an intradural dermoid in the cervico-dorsal region in a 22-year-old female manifested with subclinical infection and fluid - fluid level on imaging.

Case Report

A 22-year-old female, who underwent surgery for cervico-dorsal meningocele at the age of 3 months presented with dull aching, intermittent pain at operated site for the past 15 days. It was exaggerated by prolonged standing, sitting and relieved in a recumbent position. There was no history of weakness of limbs, trauma, fever or sphincter incontinence. The previous surgery was performed without radiological investigations, the details of which were not available. Neurological exam revealed spasticity in both lower limbs. Deep tendon reflexes were exaggerated. There was no motor deficit. Romberg's sign was positive. Magnetic resonance imaging (MRI) of cervico-dorsal spine showed a heterogeneous cystic intradural lesion between the C6 and D4 levels with compression of cord parenchyma. The solid component of the lesion had high signal intensity on T2-weighted images (T2-WI) and low signal on T1-WI, there was a large cyst within the lesion, which contained fluid - fluid level on all sequences. The supernatant was of intermediate/high signal on T1-WI and high signal intensity on T2-weighted scans. The subnatant was of lower signal on both T1-WI and T2-WI [Figure 1a–d].

Figure 1

Magnetic resonance imaging of cervico-dorsal region. (a and b) Sagittal images (c and d) axial images T1 and T2 sequences, respectively, showing heterogenous lesion with fluid - fluid level on all sequences. The solid component of the lesion had high signal intensity on T2-weighted images (T2-WI) and low signal on T1-WI. The supernatant was of intermediate/high signal on T1-WI and high signal intensity on T2-weighted scans

The patient underwent a C6 to D4 laminectomy and a near-total excision of the mass. At surgery, a well-encapsulated intradural mass was found. The mass contained pearly white material, pus and hair [Figure 2a and b]. The part of the capsule which was adherent to the dorsal surface of cord and dorsal nerve roots was left behind to prevent inadvertent injury to the spinal cord. Histologically, the lesion showed lamellated keratinous material and a diagnosis of the dermoid cyst was made. Postoperatively, she was relieved of back pain, and spasticity subsided remarkably. At follow-up after 6 years, she is asymptomatic, and MR imaging showed no recurrence of the dermoid cyst.

Figure 2

(a) Pearly content of dermoid with pus (b) The surgical specimen showing dermal sinus tract (arrow) and dermoid cyst (asterisk)

Discussion

Spinal dermoid tumors are rare, benign, ectopic slow growing tumors mostly congenital wherein during third to 5th week of embryonic development the ectoderm might get entrapped in the neural tube. Trauma has been implicated in the generation of these benign tumors later in life. Rarely, skin tissue may be forced into the vertebral canal during lumbar puncture or surgery giving rise to these cystic tumors.[1234] Spinal dermoid tumors can be intramedullary, intradural-extramedullary, or extradural. They occur predominantly in the lumbosacral region (60%), involving the cauda equina and conus medullaris, and are quite rare in the upper thoracic (10%) and cervical regions (5%).[345] They more often involve the lumbosacral region and are extramedullary, and patients harboring these cysts usually present during the first decade of life. The low incidence of dermoids in the cervical region is likely related to the embryological process of neural tube closure, which begins in the area of the neural tube destined to become the lower cervical cord and proceeds rostrally and caudally. Although rare, these lesions should be considered in the differential diagnosis when imaging characteristics are suggestive of an inclusion tumor. Preoperative MRI using fat-suppressed sequences can be helpful in distinguishing these lesions from other pathologies.

Dermoid tumors account for 0.1–0.7% of all spinal tumors with a cranial to the spinal ratio of 6:1 in adults. The prevalence of dermoid tumors in the pediatric population is much greater, accounting for 5–17% of all intradural lesions in reported series.[345] Majority of dermoid cysts present themselves with features of compressive myelopathy, bowel bladder symptoms, tethered cord syndrome, spinal deformities. Rarely, these lesions may also present with chemical meningitis from the cholesterol-laden keratin released in the subarachnoid space from a ruptured cyst leading to a foreign body type of reaction.[6] Malignant transformation of intradural dermoids has been reported by Kudo et al.[7]

Magnetic resonance imaging is an investigation of choice for diagnosing dermoid tumors.[89] Dermoid cysts usually show homogenous signal intensity, but in some cases, a heterogeneous signal pattern related to the tumor content might be observed. High signal intensity related to fat content, especially in T1-WI, provides easy recognition. MRI can also demonstrate different components of dermoid cysts. Diagnostic accuracy of MRI will increase with the use of intravenous contrast medium and fat-suppressed sequences. Bone and cartilage might be found in the tumor itself, and sometimes calcification can be seen in their walls.[8910]

Symptomatic lesions should be maximally resected with the understanding that the tumor capsule should be left behind if adherent to neural elements. Literature reveals that only 40% of dermoid cysts can be totally excised due to adherence of the cysts to surrounding neural structures, suggesting that a number of these lesions may be at increased risk for a postoperative recurrence. Partial resection, with small residual tumor tightly adherent to the nervous structures, results in the good clinical outcome and a low recurrence rate (10% or less).[11]

Dermoid tumors can be made up of 2 different pieces, one with a higher lipid content, and the other with a solid or more liquid content.[8910] Intracranial fluid - fluid levels occurring in hemorrhagic tumors and cystic lesions are well-recognized. There are three case reports of intramedullary spinal cord tumors presenting with fluid - fluid levels, two due to hemorrhage within the tumors.[1213] The third case was infected intramedullary neuroenteric cyst [Table 1].[121314] Our case is the first case report of infected intradural dermoid cyst in cervico-dorsal region showing fluid - fluid level on MRI. The high signal of the superior layer of fluid (supernatant) is most likely due to the presence of lipid or high protein concentration. The appearance of the dependent layer of fluid (subnatant) which has slightly higher signal than cerebrospinal fluid (CSF) on T1-WI and is hypo intense relative to CSF on T2-WI can be accounted for by the presence of pus.

Table 1

Reported cases of cervico-dorsal lesions with fluid-fluid level

Dermoid cyst may present with subclinical infection after many years of previous surgery. A high index of suspicion should be ascertained in a patient presenting with progressively worsening localized pain with or without motor deficits, for a variable period after surgery for spinal dysraphism, especially if previous surgery was performed without adequate radiological study. MRI is the ideal investigation to diagnose intraspinal dermoid and characterize its extent. Surgical decompression should be promptly done, and safe radical excision of the cyst should be the goal. Near or subtotal excision of the cyst wall is advocated to prevent inadvertent injury to the spinal cord, thus minimizing neurological morbidity.

Conclusion

Congenital spinal dysraphic lesions should undergo comprehensive detailed neuroimaging prior to surgery. The possibility of underlying intraspinal pathology should be investigated to prevent morbidity and enhanced neurological deficit in the long-term. Complete excision of congenital dermal sinus along with underlying intraspinal lesion is the goal. Infection should be suspected in the patients of spinal dysraphism presenting with fluid - fluid level on MRI.