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Radiol Case Rep
Radiol Case Rep
Radiology Case Reports
1930-0433
Elsevier

S1930-0433(24)00862-8
10.1016/j.radcr.2024.08.077
Case Report
Intramedullary arachnoid cyst of the dorsal spine: Report of a rare spinal cord condition
Gader Ghassen ghassgader@gmail.com
a⁎
Bahroun Sami b
Mansour Wiem a
Kharrat Mohamed Ali a
Harbaoui Ahmed c
Zammel Ihsèn a
a Department of Neurosurgery, Trauma and Burns Center, Ben Arous, Tunisia
b Department of Traumatology orthopedics, Kassab Institute of Orthopedic, Mannouba, Tunisia
c Department of Neurosurgery, Military Hospital, Tunis, Tunisia
⁎ Corresponding author. ghassgader@gmail.com
12 9 2024
12 2024
12 9 2024
19 12 57795784
2 7 2024
13 8 2024
15 8 2024
© 2024 The Authors. Published by Elsevier Inc. on behalf of University of Washington.
2024

https://creativecommons.org/licenses/by-nc-nd/4.0/ This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
Arachnoid cysts are rare subtypes of spinal cord tumors, usually found in extradural or intradural extramedullary locations. Intramedullary arachnoid cysts are exceedingly rare, with only a few cases reported in the literature. Although these cysts are histologically benign, they can cause significant functional impairment and lead to severe neurological deficits if left untreated. Their rarity presents challenges in diagnosis and management, highlighting the need for awareness and early intervention. We present a new case of a thoracic spinal cord intramedullary arachnoid cyst in a patient who displayed progressive neurological symptoms. Diagnosis was facilitated by detailed clinical evaluation and advanced imaging techniques, such as MRI. The patient underwent surgical intervention, resulting in marked postoperative improvement. This case is discussed in relation to the existing literature, offering a comprehensive review of the etiopathogenesis, clinical presentation, radiological characteristics, and therapeutic strategies for intramedullary arachnoid cysts. We emphasize the need for a tailored surgical approach to effectively decompress the spinal cord, alleviate symptoms, and minimize the risk of recurrence.

Keywords

Arachnoid cyst
Spinal cord
Neurosurgery
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pmcIntroduction

Spinal cord arachnoid cysts are uncommon lesions, generally considered benign and often asymptomatic [1]. In 1988, Nabors [2] proposed a classification system for these cysts: Type 1-extradural cysts without spinal nerve roots; Type 2-extradural cysts with spinal nerve root fibers; and Type 3-intradural cysts . Most spinal cord arachnoid cysts are extradural, while intradural extramedullary localizations are less common [1,3,4]. Intramedullary spinal cord arachnoid cysts (IMAC) are exceedingly rare, with only 27 cases of intramedullary arachnoid cysts reported in the literature to date.

In this paper, we report a new case of an intramedullary arachnoid cyst located at the cervico-thoracic junction. This case adds to the limited number of reported instances and contributes to the broader understanding of the clinical presentation, diagnostic challenges, and management strategies for this rare condition.

Case presentation

We report the case of a 58 years old male patient, with no significant medical history who presented with progressive walking impairment and bladder incontinence that had developed over the past year. Physical examination revealed spasmodic paraparesis with exaggerated reflexes in the lower limbs, significant spasticity, and proprioceptive sensory disturbances. There were no thermoalgesic impairments or sensory level deficits, and no sensory-motor disturbances in the upper limbs. Standard X-ray showed no spinal static abnormalities.

Spinal cord MRI (Fig. 1) revealed an intramedullary lesion at the T1 level, which was hypointense on T1-weighted imaging (WI) and hyperintense on T2-WI. There was no enhancement after Gadolinium injection. The lesion appeared well-defined, measuring 2 cm in length, and responsible of the enlargement of the spinal cord and the spinal canal. Given the radiologic characteristics suggestive of an intramedullary arachnoid cyst, and the patient's clinical symptoms, surgical intervention was decided. The patient underwent a laminectomy from T1 to C7. Following durotomy, the spinal cord was notably swollen. A small myelotomy allowed drainage of the cyst contents, which resembled CSF. To prevent recurrence, a transtympanic catheter (T-Tube) was placed and secured to the pia mater (Fig. 2), facilitating a cysto-subarachnoid shunt. A watertight dural closure was then performed.Fig. 1 Sagittal (A, B) and axial© sections of a spinal cord MRI on T1-WI (A) and T2-WI (B, C) showing an intramedullary lesion regarding T1.

Fig 1:

Fig. 2 Peroperative picture showing the emplacement of the T-Tube inside the spinal cord.

Fig 2:

Postoperative course was uneventful, and the patient showed an improvement of his spasticity and walking disorders. He was discharged on the third postoperative day. One month after surgery, he reported improved bladder function. A follow-up MRI (Fig. 3) performed 6 months after surgery showed a reduction in cyst size. One and a half after the surgery, the patient remains well and has not experienced a recurrence of his initial symptoms.Fig. 3 Sagittal (A, B) and axial© sections of a spinal cord MRI on T1-WI (A) and T2-WI (B, C) showing the shrinking of the cyst compared to the preoperative imaging. (D) shows the emplacement of the T-Tube (red arrow).

Fig 3:

Discussion

IMACs are very rare lesions, with only 27 cases reported to date (Table 1). Based on these cases, including our own, most patients were diagnosed either before the age of 10 (13 out of 28) or after the age of 30 (14 out of 28). There is a slight female predominance, with 16 female patients compared to 12 male patients. The actual incidence of IMACs may be higher, as asymptomatic cases and those preceding the advent of MRI technology might be underreported.Table 1 Sum up of all reported cases of intramedullary arachnoid cysts.

Table 1:Author	Age/ Sex	Symptoms	Location	Treatment	Outcome	Recurrence	
Aithala (1999)	7y/M	Severe pain in the abdomen; bladder and rectal distur- bance; weakness in the lower limbs	T1	Median myelotomy Cyst wall resection	Complete Rapid and complete	No	
Gilabert-Gonzáles (2001)	1y/F	Weakness in the lower limbs	L1-S1	Total excision of the cyst	Complete	No	
Goyal (2002)	63y/F	Severe weakness in the lower limbs (bedridden); bladder and rectal disturbance	T9-L2	Laminectomy Median myelotomy Partial excision of the cyst	Improved	No	
Sharma (2004)	10y/F	Progressive quadriparesis	C4-T1	Median myelotomy Partial excision of the cyst	Marked improvement	No	
Sharma (2005)	4y/F	Inability to walk/stand; weak- ness in the upper limbs	C4-C6	Median myelotomy Cyst was decom- pressed, and most of the cyst wall was excised	Complete	No	
Ghannane (2007)	4y/M	Weakness in the lower limbs	T3-T4	Laminectomy Median myelotomy Partial cyst wall resection	Complete	No	
Ghannane (2007)	8y/M	Weakness in the lower limbs	T3-T4	Laminectomy Median myelotomy Posterior fenestra- tion of the cyst	Good	No	
Guzel (2007)	7y/F	Severe weakness in the lower and upper limbs	C2-C4	Laminectomy Median myelotomy Partially excised with fenestration	Good	No	
Gezici (2008)	35y/F	Weakness in the lower limbs; pro- gressed to complete loss of power and
2 months of urinary incontinence	T5-T6	Laminectomy DREZ myelotomy
Majority of cyst wall excision Fenestration of the remainder cyst wall	Good	No	
Lmejjati (2008)	12y/F	Weakness in the lower limbs	T3-T4	Median myelotomy Marsupialization	Full recovery	No	
Medved (2009)	1y/M	Bladder and rectal disturbance; inability to walk/stand	T5-T6	Hemilaminectomy DREZ myelotomy Marsupialization	Complete	No	
Diyora (2010)	45y/f	Severe pain; weak- ness in lower limbs; progressed to para- plegia with urinary and fecal incontinence.	T4-T5	Laminectomy Midline myelotomy Cyst wall partially excised	Improved	No	
Kataria (2012)	9y/F	Back pain; weakness in the lower limbs; bladder and rectal disturbance	Thoracolumbar	Laminectomy Median myelotomy
Partial excision of the cyst	Complete recovery	No	
Kataria (2012)	40y/F	Weakness in the lower limbs; bladder and rectal disturbance	L1	Partial excision of the cyst wall	Good	No	
Bond (2012)	2y/M	Back and lower limbs pain	T10	Fenestration of the cyst	Good/ remission	No	
Rahimizadeh (2013)	58y/F	Weakness in upper and lower limbs	C6-T2	DREZ myelotomy Wide fenestration with partial excision of the cyst wall Cervicothoracic in- strumentation from C3 down to T2 was done	Improved	No	
Novegno (2014)	31y/F	Back pain; weakness in the lower limbs; bladder and rectal disturbance	T11-T12	Median myelotomy Fenestration
Partial excision of the cyst	Complete	No	
Thakar (2016)	64y/M	Weakness in lower and upper limbs	C6–T1	Cyst wall excision	Not available	Not available	
Alugolu (2016)	54y/F	Weakness in the lower limbs; paresthesia	T8-T12	Laminectomy Partial removal of cyst wall	Good	No	
Panwar (2019)	40y/M	Numbness in bilater- al lower limbs	T11-T12	Median myelotomy Incomplete removal of cyst wall was done	Pain relieved completely	Suggestive of recurrence after
11 months	
Panwar (2019)	45y/F	Paresthesia and spasticity in lower limbs	T9-T10	No available ap- proach
Cyst wall excision	Pain relieved completely	No	
Shaaban (2019)	32y/M	Bladder and rectal disturbance; impo- tence; repeated falling	T6-T8	Median myelotomy Partial excision of the cyst	Improved	No	
Ichinose (2020)	4y/M	Weakness in the lower limbs; bladder and rectal disturbance	C2-C3	First fenestration of the cyst
Median myelotomy Second excision of the cyst	Good	Yes, after 27 months	
Aljameely (2020)	47y/F	Weakness in upper and lower limbs; bladder and rectal disturbance	C3-C5	DREZ myelotomy Cysto-subarachnoid shunt	Complete recovery	No	
Diyora (2022)	45y/F	Difficulty in walking	Craniocervical Brain to C7	After 2 failed trials of needle aspiration, cysto-subarachnoid shunt	Complete recovery	Yes, after 4 months	
Thakur (2021)	2y/M	Decreased sensation over the gluteal re- gion along with per- sistent dribbling of urine	T12-L1	Laminotomy Median myelotomy marsupialization	Improved	No	
Afana (2023)	2y then 32y/M	Back pain and pro- gressive paraparesis	T7-T8	Cyst drainage and fenestration Partial excision of cyst wall	Improved	Yes, after 13 years	
Present case	58 y/M	Progressive paraparesis	T1	Cyst drainage and cysto-subarachnoid shunt	Improved	No	

Various hypotheses have been proposed regarding the etiology of IMACs. Most reports suggest a congenital origin due to the higher incidence in children. Additionally, pediatric cases are often associated with other central nervous system malformations, and some cases are familial [5]. Some authors [6,7] have suggested a link between IMACs and dysraphic anomalies of the spinal cord. IMACs are thought to arise from secondary cystic development of atypical intramedullary arachnoid granulations which become trapped in various locations, leading to CSF production and cyst formation [8,9]. This misplacement results in embryonic malformation and subsequent cyst development. On the other hand, acquired IMACs may result from arachnoiditis caused by infection, spinal surgery, lumbar puncture, or epidural anesthesia [4,10].

Clinical presentation is due to the compression of the spinal cord and nerve roots, and mainly depends on the volume and location of the cyst [11,12]. Most patients present with weakness or motor impairment, back pain, and varying degrees of sensory and sphincter dysfunction. It is noted that the majority of patients experience a progressive onset of symptoms, with rapid neurological deterioration attributed mainly to IMAC expansion. Some authors discuss potential “trigger points” for this deterioration, but this hypothesis remains uncertain, even though some patients have shown neurological worsening following subsequent infection [1,9,10].

X-rays may be helpful in showing spinal canal enlargement, vertebral scalloping, or spinal static disorders. MRI is the gold standard for the diagnosis, as well as for studying the extent, size and nature of the cysts. Arachnoid cysts have the same intensity as the CSF on T1 and T2 weighted images [4,5]. However, T2-WI may show heterogeneous signal intensity, depending on the flow effect in the cyst fluid [3,10]. In reported cases, IMACs are mainly located in the thoracic spinal cord (15 cases). Cervical localizations have been found in 5 cases, and 3 patients had arachnoid cysts at the cervico-thoracic junction.

Despite the “typical” appearance on MRI, IMACs can be misdiagnosed due to their rarity, and some differential diagnoses include post inflammatory cysts, neuro-enteric cysts, cystic teratomas, and post traumatic cysts [1,9].

Most patients are diagnosed after developing neurological symptoms, which often necessitates surgical management. The timing of surgery is crucial; early intervention after symptom deterioration is key to achieving a better outcome [11].

Surgery is typically performed through a posterior approach [11]. The posterior midline myelotomy is the traditional pathway to access the cyst, but some authors have used the dorsal entry zone approach for anterior and unilateral IMACs [13,14]. Various management techniques have been reported, including simple aspiration, fenestration, removal of the cyst wall, marsupialization, and cysto-subarachnoid shunting [13,15,16]. Most authors advocate for wide fenestration of the cyst with partial or complete excision of the wall [15,16]. In our experience, we found that excision of the cyst wall is difficult and risky due to its adherence to the cord parenchyma. Therefore, we performed a cysto-subarachnoid shunting using a transtympanic catheter, also known as a "T-Tube."

Most reported cases emphasize positive outcomes after surgery. However, among these patients, 4 experienced recurrence after various periods: 27 months after cyst fenestration [13], 4 months after aspiration [17], 11 months after incomplete wall resection [18], 13 years after an unspecified procedure [11]. Despite these encouraging results, the risk of cyst recurrence, adhesions and fibrosis remains, highlighting the importance of long term follow ups.

Conclusions

IMACs are exceedingly rare lesions with a limited number of reported cases. They present significant diagnostic and therapeutic challenges due to their rarity and the potential for severe neurological impairment. Our case adds valuable insight into the clinical presentation, diagnostic process, and surgical management of IMACs. Early diagnosis and timely surgical intervention are crucial for achieving optimal outcomes. Despite generally positive postoperative results, the risk of cyst recurrence requires long-term follow-up. Continued reporting and analysis of new cases are essential to enhance our understanding and management of this rare condition. Future research should focus on refining surgical techniques and improving long-term outcomes for patients with IMACs.

Patient consent

Written informed consent was obtained from the patient for publication of this case report and accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal on request.

Competing Interests: The authors do not have any conflicts of interest to declare concerning this article.
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