Intradural epidermoid cyst with atypical magnetic resonance imaging and clinical presentation

Introduction

Epidermoid cysts are rare benign neoplasm within the neuraxis, which are commonly located in the intracranial region and account for <1% of all intraspinal tumors.^[1,2] In 1835, Cruveilhier was the first to describe epidermoid cysts, calling them tumeurs perlées (pearly tumors).^[3,4] Epidermoid cysts can be congenital or acquired. Congenital epidermoid cysts are frequently found in association with spinal dysraphisms such as syringomyelia, dermal sinus, and spina bifida, while the most common etiology for an acquired cyst is repeated lumbar puncture.^[2,5]

Although epidermoid cysts can be extradural, intradural or extramedullary, or intramedullary in the spine, the tumors are often intradural and extramedullary in the lumbosacral region.^[6]

Neurologic symptoms such as progressive paraparesis, motor-sensory complaints, and sphincter troubles cause great distress.^[2,4,5,7,8] Patients with an epidermoid cyst usually suffer for a long time with symptoms, for an average time of 6 years, due to their slow-growing nature.^[2,4]

Magnetic resonance imaging (MRI) is an effective tool in the diagnosis of intraspinal epidural cyst. On MRI, the tumor is usually isointense or hypointense in T1-weighted (T1W) images and hyperintense in T2-W images, and the cyst content has the same signal as the cerebrospinal fluid.^[9,10,11]

We present a case with atypical clinical findings and MRI shows finding of being hyperintense in T1W image and isointense in T2W images.

Case Report

A 27-year-old male presented with tingling and weakness of the left lower limb since last 6 months. Tingling appeared 6 months back and for last 2 months felt weakness and limp while walking in the left leg. On examination, he had no cutaneous lesions on back; he had power Grade 5 in bilateral lower limbs. Sensations were intact. Left lower limb toe walking was unsteady. Reflexes of both ankle and knee were depressed bilaterally. No sensory involvement. No bowel bladder involvement. Perianal sensations were intact.

His MRI showed heterogeneous hyperintense lesion at cauda equina of spine at L1-L2 level on T1W and isointense on T2W. It showed minimal heterogeneous postcontrast enhancement. It was displacing spinal nerve roots at this level. Screening of spine revealed no lesions anywhere else in the spine and no spinal dysraphisms [Figures 1-3 and 4].

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Figure 1

T1-weighted sagittal magnetic resonance imaging showing a solitary lesion

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Figure 2

T1-weighted sagittal magnetic resonance imaging showing hyperintense isolated lesion behind L1-L2 bodies

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Figure 3

T2-weighted sagittal magnetic resonance imaging showing isointense lesion

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Figure 4

Postcontrast minimal heterogeneous enhancement

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Intraoperatively, L1-L2 midline laminectomy was done, an obvious bulging of the cord was seen at the involved level. Durotomy was done; the tumor sheath was attached to nearby rootlets. We tried to separate the sheath from the roots, but they were intimately attached and removing the attachment threatened severing the roots. Hence, we opened the sheath and debulking was done. Pearly white and flaky pieces of tumor pieces were removed. After near complete removal, durotomy was closed, and layer by layer skin closure was done.

Histopathologic examination showed cystic lesion lined by keratinized stratified squamous epithelium and lumen filled with keratinous material. The stroma showed fibro-adipose tissue [Figure 5].

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Figure 5

Histopathologic examination showed cystic lesion lined by keratinized stratified squamous epithelium and lumen filled with keratinous material. The stroma showed fibro-adipose tissue

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Postoperatively, the patient had no new neurological deficit. One month later, his power in bilateral lower limbs remained Grade 5. His limp reduced but still he has difficulty to toe walk over left limb. His tingling has reduced only mildly.

Discussion

Epidermoid cysts in the spine are thought to arise from one to two possible origins: congenital or acquired.^[12] Congenital epidermoid cysts, which are more common and often associated with other spinal dysraphisms, are caused by the anomalous implantation of ectodermal cells during closure of the neural tube between the 3^rd and 5^th weeks of embryonic life.^[2,13,14] The number of acquired cysts has decreased significantly in recent years. They are attributed to the displacement of epithelial tissue secondary to a previous lumbar puncture or trauma.^[15,16,17]

The case we present is of congenital in origin as he had no history any trauma or lumbar puncture. He neither had evidence of other spinal abnormalities.

Symptoms arising from epidermoid cysts vary with the level of involvement but do not differ from other space-occupying lesions in the spinal column. Signs and symptoms at presentation are usually neurological such as progressive paraparesis, sensory loss, urological manifestations, and back/leg pain. The slow growth of epidermoid cysts often leads to a delay in their diagnosis: Duration of symptoms before diagnostic recognition may extend for many years. Due to this, the symptoms may often arise in early or middle adult life.^[12]

MRI is an effective tool for the diagnosis of an intraspinal epidermoid cyst. X-rays often show a normal image and computed tomography can only display the location and outline of the tumor. On MRI, the tumor is usually isointense or hypointense in T1-W images and hyperintense in T2-W images and the cyst content has the same signal as the cerebrospinal fluid.^[9,10,11] However, these signal characteristics are not always constant, and some variations have been reported in the literature.^[10,18,19] Our case shows atypical finding of being hyperintense in T1W image and isointense in T2W images. Similar MRI finding in one case was reported by Yin et al.^[20]

The pathologic examination is vital for the final diagnosis of an epidermoid cyst. Histologically, epidermoid cysts are composed of lined stratified squamous epithelium supported by an outer layer of collagenous tissue. Progressive desquamation of keratin from the epithelial lining toward the interior of the cyst produces a soft white material rich in cholesterol crystals.^[2,19,21,22] The absence of skin adnexa is the key to differentiate one from a dermoid cyst.^[2,22]

Given their indolent, benign nature, asymptomatic epidermoid cysts should be managed conservatively. Surgical excision is essential for lesions with symptomatic progression and where imaging shows that neural elements are compressed.^{[19,20,23,24]} Although radiotherapy has been used in one case with repeated relapses of epidermoid cysts, achieving a relatively good result, this treatment should only be used for patients who refuse surgery or are inoperable for medical reasons.^[25] Undoubtedly complete excision without neural damage is the goal of treatment. Emptying of the cyst material can be performed easily, but the intimate adherence between the capsule and the spinal cord makes this goal difficult. Hence, subtotal excision tends to be the more common surgical pattern for avoiding possible neural damage.^{[10,11,12,21,26,27]} Subtotal excision also causes great distress for patients and doctors because debris from the tumor may cause an early relapse of symptoms and the spread of cyst contents can cause foreign body reactions and severe complications.^{[2,9,11,21,24,25]}

Conclusion

Given the atypical presentation of the MRI causes confusion in the diagnosis. Sometimes due to slow growing nature it's very late that such a tumor is diagnosed, that is after the patient has some neurological deficit. Histopathologic examination remains authoritative in confirming the diagnosis. Total excision of tumor is desired but as it may cause damage to roots and increase neurodeficit, debulking and subtotal removal may be enough. Recurrence if present must be dealt with radiotherapy.