The spinal arachnoid cyst in children – a diagnosis challenge

SUMMARY

Introduction: Arachnoid spinal cyst can be isolated or associated to intracerebral arachnoid cysts. Intraspinal arachnoid cyst can present at different levels of the spinal cord  and so symptomatology diff ers due to level of compression or involvement of the spinal structures and the extension of the lesions. Objectives: We want to bring in attention a pathology which is not very frequent but also is not very rare so in the clinical practice the neurologist can met this pathology. We want to off er an easy and rapid tool fot the management in this pathology. Material and methods: We searched in the classic literature as also the specialised sites (Pubmed, Google Academic, Medline)  Results and discussions: Modern imagistic methods are complementary and the intraspinal cystic lesinos can be investigated in multiple ways, so to have a more clear picture about them. Differential diagnosis is essential because the clinical judgement and case management are very different due to different causes (infections,vascular pathology) or when genetic diseases are in relation  to them, or when we discuss about metabolic heredopathies.

Keywords: arachnoid spinal cyst, classic literature, differential diagnosis.

INTRODUCTION

The spinal arachnoid cyst can exist isolated or in association with other intracerebral arachnoid cysts. The intraspinal arachnoid cyst pathology can be present at different levels of the spinal cord, therefore symptomatology may differ due to level of compression or involvement of the spinal structures and the extension of the lesions.

OBJECTIVES

We want to bring to attention a pathology that is not very common but, nonetheless, fairly frequently encountered in the practice of the neurologist. Our aim is to offer an easy and rapid tool for the management of this pathology.

MATERIAL AND METHODS

In our research, we read the domain-specific literature (books, journals, articles, studies) and we used domain-specific sites such as Medline, PubMed, Google Academic; we also performed meta-analyses regarding the arachnoid cyst pathology.

RESULTS AND DISCUSSIONS

Modern imaging methods complement each other and give a broader picture of cystic intramedullary pathology. The differential diagnosis of these cysts is essential because their approach differ when infections, vascular pathology or genetic diseases are involved.

DEFINITION

Arachnoid cysts can be defined as a herniation of the arachnoidian membrane due to a Dural defect, which can be either congenital or acquired [1]. They contain fluid with a composition similar to the cerebrospinal fluid. Arachnoid cysts can be found on the brain or on the spine.

A BRIEF HISTORY

Arachnoid cysts are of interest for researchers in the publication of numerous scientific treatises even since the nineteenth century. The literature disseminates the pathological phenomenology of cysts, both according to the physical and social characteristics of the patients and to the impact of the medical pathology on the patient’s health through the association of other psychosomatic comorbidities. Figure 1 presents a meta-analysis based on the typology and location of arachnoid cysts approached by specialists within their scientific research.

INCIDENCE

The spinal arachnoid cysts are present in a percentage of 1% of the total number of spine-related tumours in children, whereas spinal extradural ones are more present at the level of the thoracic spine (65%). The ratio of arachnoid cysts regarding their presence in boys or girls is 2.7:1. The children were monitored for 22 ± 10.9 months by researchers.

Garg et al from 2009 until 2012, who published the results of their research in 2017. Figure 2 presents the disease frequency distribution according to the gender of the patients and to the domain-specific literature studied [6, 7].

The ratio between the intracranial arachnoid cysts and the medullary arachnoid cysts is 17:125. They can occur at any age and generally occur in the second decade of life, but 1/3 of the cases occur in childhood [8]. Figure 3 represents the scaling of the above-mentioned arachnoid cyst distribution ratio.

LOCATION

Usually the cysts are located at the level of the thoracic spine, but they may be also found at the level of the sacral region of the spine, especially in men who are between 20 and 50 years of age when the cyst is discovered, in children the cases being extremely rare [7]. The vast majority of the cysts that are located at the level of the thoracic spine are on the posterior aspect of the cord, whereas anteriorly located arachnoid cyst are exceptional, and they most often occur in the cervical spinal region [9]. Anan M et al describe in 2010 the case of a 5-year-old girl with an intradural cervical arachnoid cyst [10].

The cysts located at the level of the medium thoracic spine and those located at the level of the thoracolumbar spine, are most often than not posterior. However, these localizations appear in 30-50 year-old women. In percentage terms, the arachnoid cysts occur in the thoracic region in 65% of the cases, in the lumbosacral region in 13% of the cases and in the thoracolumbar region in 12% of the cases. Other locations are in the sacral region, 6.6%, and in the cervical region, 3.3%, as described by Chellathurai A et al. in 2018 [2]. Figure 4 represent the distribution of the spinal localization of arachnoid cysts after Chellathurai A et al.

The meta-analysis of the spinal arachnoid cyst diagnosis case load (Gezici) presents interesting conclusions regarding the correlation between cyst localization and the progressive symptoms of tetraparesis. In 2008, Gezici et al. described the case of a 2 ½-year-old boy with an intradural cervical arachnid cyst situated at the cervicomedullary junction at C7 and which caused progressive tetraparesis [11]. Figure 5 shows the distribution of the symptoms associated with the arachnoid cyst according to Gezici’s study.

Figure 6 is a meta-analysis of patient age distribution according to Gezici’s analysis, which shows the fact that, both in children and in young people, there is a significant representativeness of certain spinal arachnoid cysts.

Figure 7 analyses gender distribution in Gezici’s study, revealing a male prevalence as in all other spinal arachnoid cysts.

Spinal arachnoid cysts extend over a length of <1 to > 10 vertebral bodies, and those that are at the outer extremity of this stretch are called giant cysts [12].

Pathophysiology: The spinal arachnoid cyst can be the result of arachnoiditis, which, in turn, results from processes that follow a subarachnoid haemorrhage or meningitis associated with infectious myelitis [9].

The ventral displacement of the spine may be caused by the transdural herniation of the spine or by the existence of arachnoid cysts, which causes progressive myelopathy. Changes to septum posticum may also lead to intradural arachnoid cysts [2]. Septum posticum is a structure that extends from the cervical region to the lower thoracic region of the spine. It divides the subarachnoid medullary spinal space into two [13]. This fact was also postulated by Perret et al [14]. In children, a spontaneous phenomenon of spinal arachnoid cysts may occur, which can then also disappear spontaneously [15]. Extradural arachnoid cysts also have a thin fibrotic membrane like other arachnoid cysts. Nayak R et al. also described 7-year-olds with multiple arachnoid cysts in 2017 [16]. When the cysts communicate by means of a narrow pedicle, the valve mechanism, by which the cerebrospinal fluid enters the cyst and develops pressure, is incriminated. The osmotic gradient between the cystic structure and the subarachnoid space is another mechanism used to regulate the pressure in the cyst. But also the degenerated cells from the cystic membrane layer can generate osmotic pressure that has an effect on the arachnoid cyst’s inner structure. On the other hand, inside the cyst, proteins of high oleic mass are accumulated, which cannot cross the cystic membrane. An important role is also played by the active secretion of cells from the cyst membrane [17]. Table I shows the meta-analysis of the pathophysiological phenomena described by researchers regarding spinal arachnoid cysts, which clearly indicate the fact that intracystic pressure plays a major role in the cysts’ later evolution, and subsequent research has focused on the management of this pressure.

CAUSES

The arachnoid cysts may appear secondary to infectious syndromes, also occurring after subarachnoid haemorrhage, or in the context of metastasis or spinal surgery [18]. In the extradural arachnoid cyst at the sacral level we may also encountered an association with rare diseases also such as medullary dysraphism (diastematomyelia), spinal cord dissection. Between the two parts of the marrow there is a sagittal septum made up of fibrous or cartilaginous tissue. This phenomenon was described by Habibi Z et al in a study, carried out between 2008 and 2014, on 73 patients with diastematomyelia malformations, out of which 7 children had this rare association with a sacral arachnoid extradural cyst. Moreover, siringomyelia is associated with diastematomyelia in 25-40% of the patients [19].

The meningocele is also associated with the spinal arachnoid cyst [20]. A rare case of association between a thoracic spinal extramedullary intradural dorsal arachnoid cyst and an intrathoracic myelomeningocele at the same level as the cyst was described by Zheng-Si lao et al. in 2010 in a 9-yearold boy. The same authors quote Baysefer et al. (2011), who describe an association between the thoracic meningocele and the thoracic spinal arachnoid cyst in a 2-year-old child [21].

The spinal arachnoid cyst occurs in the context of the Marfan syndrome or dural ectasia due to the low resistance to traction forces of the modified collagen fibres [22]. The medullary arachnoid cyst may be associated with posterior fossa glioma, which may develop slowly, thus the cyst being asymptomatic; this phenomenon was studied by Suo-Palosaari et al. in 2016. The same authors also described a spinal hyperpigmentation in the external part of the spinal arachnoid cyst [23]. In addition, a case report was published by David K. Su in 2012 regarding the association between siringomyelia and the spinal arachnoid cyst [24]. In 1980, a report was published by Schwartz et al. regarding a rare syndrome involving the spinal arachnoid cyst, the (changes in implantation of genes), partial ectropion of the lower eyelid as well as lymphedema that may have its onset at the age of childhood or adolescence; this syndrome is able to distichiasis group more members of a family. It is assumed that the disorder is dominantly autosomal, with variable phenotypic expression, in which the affected members have two or three of the features described [25]. The spinal arachnoid cyst may also be associated with neurocutaneous melanocytosis [26].

Iatrogenic: After the surgery of a sacral lipoma, a sacral arachnoid cyst may appear [27].

Figure 8 synthesizes the more common causes of spinal arachnoid cysts, but also rarer cases mentioned in the literature by various researchers.

CLASSIFICATION

Sacral extradural arachnoid cysts are classified into 3 types by Nabors et al:

– Type 1. Extradural meningeal cysts containing non-neural tissue are divided into extradural (type A) and sacral meningocele (Type 2, TC)

– Type 2. Extradural meningeal cysts containing neural tissue, which contain, in their turn, fibres from the spinal nerves (Type 2, TC)

– Type 3. Extradural meningeal cysts [2,28].

Type 1 extradural cysts usually communicate with the intradural subarachnoid space, but there are very rare cases in which these cysts are noncommunicating [29]. Multiple cysts were described in an 11-year-old child by Kumar et al. [1].

DIFFERENTIAL DIAGNOSIS

The differential diagnosis is performed with synovial cysts, but also with The Tarlov cysts that are located at the sacral level and can be caused by different mechanisms [28]. Tarlov cysts may be found along the spinal nerves and appear like fluid-filled sacs. They can induce sensory symptoms such as paraesthesia but also pain as well as motor symptoms such as spasticity, hypertonia but also a certain degree of weakness in life. Tarlov cysts are found accidentally in 4.6-9% of the cases if an MRI is performed, whereas sacral cysts have a rate of 1% in which they become symptomatic [30]. Other confusing cysts mentioned in the literature may be the menigocele, dermoid cysts, encephalic diverticula, which are formed along the roots of spinal nerves, and the cystic schwannoma [7]. Dura mater thickening, known in the international literature as the arachnoid spinal web, occurs in the form of arachnoid membrane trabeculae stretching from the pial membrane to the dorsal part of the spine. Some consider these clumps variants of the arachnoid cyst [31].

This thickening of the arachnoid membrane can cause siringomyelia when associated with a malformative syndrome such as the Dandy Walker syndrome, comprising cerebellar vermis dysgenesis and a posterior fossa cyst, as described by Lee HC et al., n 2017, in a 10-year-old child [32]. The medullary neurenteric cysts are rare but their localization is predominantly anterior and, when they are located behind the marrow, then other types of spinal dysraphism are associated [33].

SYMPTOMS

Major symptoms include myelopathy, radiculopathy. They can be silent at first, the first symptom is pain, followed by other compression symptoms [34]. Symptoms of compression may include symmetric motor deficit and, depending on the compression degree, the motor deficit is usually below the level, including paraparesis, the pyramidal syndrome and the Babinsky bilateral reflex, to which exaggerated patellar osteotomy reflex and exaggerated Achilles reflex are added [28].

When located cervically, they can cause torticollis that may or may not be accompanied by progressive tetraparesis, but they may also cause the Horner syndrome, or sensory upper limb disorders. This case was described in a 2.5-year-old child by Alkan G in 2016. The torticollis can also occur in case of tumours, and the Horner’s syndrome also occurs in children with eye disorders or children may also be confronted with infections or the subluxation of the atlanto-axial joint [35, 36].

In addition, the cervico thoracic spinal arachnoid cysts may lead to a brachial plexus palsy  [37]. Uncommon misleading symptoms may be recurrent abdominal pain when the cyst is localized at T11-L2 [36]. Rare symptoms, but that must not be neglected, are constipation and urinary bladder dysfunctions, as described by Medved et al., in 2009, in an 18-month-old child, but associated with subsequent loss of walking, the child having a T5-T6 thoracic cyst. The correct diagnosis of the disease is essential, that is why an MRI is performed in order to conform the cyst and the subsequent treatment consists in easing the symptoms [38]. Another associated symptom may be the flatfoot, which is characteristic to certain spinal arachnoid cysts [39].

INVESTIGATIONS

The simple thoracolumbar X-ray can also provide important data regarding the existence of abnormalities in the spinal canal, which leads to the extension of the investigations, thus one may notice an enlargement of the interpedicular space, reduced pedicles as well as a higher foramina, fact that suggests the enlargement of the spinal canal, and hypointense lesions in T1 [40], and hyperintense lesions in T2, which have enhancement contrast [28]. A cystoscopy, an MRI or regular blood tests may be performed when a urinary bladder dysfunction occurs. In new-borns, who have a cutaneous stigmata, which may occur in 2.2-7.2% of all new-borns (e.g. hair), a spine ultrasonography with a 7-12 hz transducer GE Logiq S8 may be performed, and if there are any modifications, a spine MRI is further performed [41]. The CT myelography, as well as the cinematic MRI, are important for an accurate diagnosis and make communication between the cyst and the subarachnoid space obvious [2, 6]. The myelography is also important in detecting the level of the cerebrospinal fluid blockage in order to make the most accurate surgical decision. In this respect, Baatzdorf is quoted by Mauer et al. in an article from 2007, where the cardiovascular flow measurement with phase-contrast MR imaging is mentioned. The velocity limit is 3 cm / second but it can be increased to 5.8 cm / sec to 10 cm / sec. The study comprised 320 patients with syringomyelia, and the blockage was observed in 33 patients, out of which 8 had changes in the arachnoid membrane and the arachnoid cysts were located several levels below the level of the syringomyelia [42]. The ultrasonography helps in diagnosing the Tarlov cysts that are separated from the ovary and are immobile when breathing [30]. The ultrasonography also helps in highlighting the cyst’s pulsations in the arachnoid cyst sac at the level of its ends, where the excision of the cystic mass is performed [12].

T2 images are clearer, especially in the MRI 3 Tesla, which removes the arachnoid cyst delimitation artefacts. The CT is used less frequently, but it can show aspects of bone margins and helps to visualize the dimensions of the spinal canal. The CT also shows the erosive processes of the pedicles and the increase in the foraminous diameters, the last modifications being characteristic of extradural arachnoid cysts [18]. The electromyography is useful when spinal nerves are involved, for example, in the sacral extradural arachnoid cysts [43]. The histopathological examination of the cystic membrane is performed when arachnoid monolayer cells are found positive for epithelial membrane antigen [36].

SURGERY

The most commonly used surgical procedures are laminotomy, laminectomy and durotomy. Extradural cysts are excised, whereas intradural ones are fenestrated [17]. Extradural cysts are first operated on with laminoplasty and then the cyst is excised [6]. Surgical intervention is beneficial when it is necessary. This fact is demonstrated by a study conducted on 18 patients with intradural arachnoid cyst, out of which 13 were symptomatic and were operated on, and in 10 of them the symptoms completely disappeared [44]. The injection of Gentian violet in the subarachnoid space near the suspect clump is a method of tracking the cerebrospinal liquid flow, the Gentian violet playing the role of a tracer [31]. For the extramedullary arachnoid cysts, with intradural localization, located at the subaxial medullary level and stretching to the cervicothoracic junction, a long lateral procedure, described by Singh H. et al in 2017, was used in two cases of children with spinal arachnoid cyst. The authors quote Heroscaare, who described this procedure for the first time in 1986. The procedure has real advantages because it preserves the midline, including the spinal ligament and thus avoids the kyphosis that may occur after laminectomy [45]. Intradural cysts can be operated on with CT or MRI guidance [46]. Different materials are used to fully close the communication between the subarachnoid space cysts and the extradural cysts. These most common materials used are the suture thread or oxidized cellulose, but human tissues can also be used, such as fat, or synthetic materials, such as an absorbent material, which can help in recovering the dura [18].

A study conducted by Kaufmann et al, in 2010, on 27 cases of spinal cord injury, out of which three were children with arachnoid cysts, showed that dura closure can be also safely done with the help of nonpenetrating titanium clips with an Anastoclip vessel system, LeMaitre Vascular, Inc. The system can also be used in gynaecology, urology, in plastic surgery and vascular surgery [47]. Intradural endoscopy is a method for the prevention of spinal arachnoid cyst surgery. It offers better visibility of some details that can escape during other surgical procedures [48]. Arachnoscopy is a useful method for visualising the adhesions of the subarachnoid space, fact underlined by Mauer in 2011. Sophisticated statistical methods have established that the dimensions of an endoscope used in the spinal intradural space is 2.5 mm in diameter [14]. Gul et al describe, in 2009, the case of an 8-year-old boy who had an intradural noncommunicating extramedullary cyst, stretching on several levels, that was extracted, and the laminoplasty contained only one level [49]. Progressive thoracic kyphosis is a common complication in children after a laminectomy. As far as laminoplasty is concerned, the authors described the case of an 11-year-old girl on whom this procedure was performed due to the presence of an arachnoid cyst, who, after three months, developed a severe thoracic kyphosis, with the maximal point where the laminoplasty was performed. Normally, laminoplasty is a method that allows a wider exposure of the spinal elements that are compressed, allowing and maintaining the integrity of the posterior elements, and allowing the surgeon to restore the paraspinal muscles, and this is why it was considered as being superior to laminotomy, precisely because this would better prevent the deformities of the spine, which is immature and is in full growth and development. Regardless of the procedure used, it is essential to perform serial X-rays until the skeletal maturation is completed [50]. Particular cases may need several approaches. Kahraman et al. described in 2008 the case of a giant extradural arachnoid cyst stretched on several levels in a 9-year old boy. The cyst ranged from T4 to L3. This cyst was first shunted cystoperitoneally and because the operation failed and the child developed subsequent symptoms, he suffered a second surgery and then the cyst was excised altogether. After such cystoperitoneal surgery, fistulas may also be formed, which may require external lumbar drainage. But after the radical surgeries involving complete cyst removal, neurological symptoms are often resolved [51]. An innovative technique was introduced by Dev. et al. in 2008, called cystectomy, for a thoracolumbar extradural cyst spread across several levels, T7-L1, in a 9-year-old boy. This technique is minimally invasive. It started at the caudal end of the cyst, with a minimal laminectomy at L1 level and with local anaesthesia and with small 1-cm incisions at the level of the cystic membrane, and then, at the level of the thecal sac; afterwards, the two cysts were opened and then a stoma was made between the two with 3-0 polyglactin and so the cyst communicated with the thecal cavity. This method avoided unnecessary dissections of surrounding tissues, there were the difficulties in dissecting around the cyst and making an uneasy excision [52].

CONCLUSIONS

The problem of arachnoid cyst pathology is of interest not only because of the frequency of the disease but also because of its effects on the patient’s health condition, with an aggravating cause in association with various comorbidities. In view of the above mentioned facts, we noticed rich scientific research in the studied field, published by specialists in the international literature, which allowed us, by means of a meta-analysis procedure, to draw conclusions about the correlations between the location of the spinal arachnoid cysts, their symptomatology and surgical treatment. We believe that the surgical procedure should be performed during the crisis period as soon as possible after diagnosis by applying effective procedures to facilitate the remission of the disease.

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