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CorrespondenCe

Introduction

Adhesive spinal arachnoiditis and syringomyelia are infre-quent but severe late complications of subarachnoid hemorr-hage (sAH). In 2 large representative series of patients treated for non-traumatic syringomyelia associated with subarachnoid scarring sAH was the etiology behind only 1 out of 55 patients (1.8%) and 3 out of 32 patients (9.4%), respectively [1, 2]. In this article two cases are described, the pathophysiology of this condition is discussed and the importance of early diagnosis in order to assure the best possible prognosis is emphasized.

Case Reports

Patient 1 A 57-year-old woman presented with sAH from an aneurysm of the anterior communicating artery. The sAH magnitude was Fisher grade 3 on a computed tomography (CT) head scan which also showed ventricular enlargement. The Hunt and Hess grade was IV. A right frontal external ventriculostomy was placed. The aneurysm was occluded using endovascular coiling 15 h after bleeding. The patient had 24 days in-hospital care including 12 days in the neu-rosurgical intensive care unit. After 11 days the ventricu-lostomy was removed and a lumbar drain was inserted to allow cerebrospinal fluid drainage for 2 additional days. The patient was discharged to a rehabilitation clinic and a 3-month follow-up CT scan showed normal ventricles and no cerebral parenchymal lesions. The patient showed a good

recovery and returned to normal work 10 months after the aneurysmatic bleeding. Approximately 18 months after sAH the patient presented with progressive gait ataxia, sen-sory disturbance (hypoesthesia for temperature and touch and paresthesia at thoracic dermatomes), lower limb motor deficits and difficulty in emptying of the bladder and bowels. Magnetic resonance imaging (MrI) revealed arachnoiditis and syringomyelia (Fig. 1). The patient was scheduled for elective surgery. In the meantime a routinely scheduled fol-low-up angiography showed stable, complete occlusion of the aneurysm. At 22 months after sAH the patient was trea-ted by explorative laminectomy at levels T4–T8. extensive adherences found around the spinal cord were fenestrated and two shunt catheters were inserted into a subarachnoid cystic lesion situated ventrally to the spinal cord and into the intramedullary syrinx (Fig. 2). The shunt catheters were attached to a James lumbar peritoneal shunt joint (Codman & shurtieff, raynham, MA) and a distal catheter was placed in the peritoneal cavity. The patient’s leg motor function and thoracic sensitivity improved after this operation. However, the previous symptoms returned rapidly 8 months after sur-gery, this time accompanied by increasing thoracic pain. A spinal MrI study showed expansion of the syrinx down to the L1 level. The shunt system was revised and a new abdo-minal catheter with zero resistance was placed. post-opera-tively, leg symptoms improved but painful paresthesia in the thoracic dermatomes persisted.

Patient 2 A 65-year-old woman presented with sAH from a fusiform, dissecting aneurysm in the retrotonsillary seg-ment of the left posterior inferior cerebellar artery (pICA) which had been treated elsewhere with embolization of the pICA at the aneurysm site using n-butyl-2-cyanoacrylate. embolization resulted in a small cerebellar infarction with permanent lower limb ataxia on the left side. The patient

Clin neuroradiol (2012) 22:169–173doI 10.1007/s00062-011-0082-5

Subarachnoid Hemorrhage-associated Arachnoiditis and Syringomyelia

J. Eneling · S. Boström · S. Rossitti

s. rossitti, Md, phd () · J. eneling · s. Boström department of neurosurgery, University Hospital, 58185 Linköping, swedene-mail: sandro.rossitti@lio.se

received: 16 January 2011 / Accepted: 18 May 2011 / published online: 18 June 2011© springer-Verlag 2011

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presented 2 months later with sudden central facial palsy on the left side and a small lacunar infarction at the right cap-sula interna was diagnosed on a head CT scan. The patient made a fair recovery with moderate disability and was inde-

pendent in activities of daily life but 6 years after sAH the patient developed lower limb motor and sensory deficits which progressed slowly. In this period the patient moved to a nursing home and a head CT scan showed a normal ventri-cular system and parenchymal reduction at the sites of earlier infarction in the cerebellum and at the right capsula interna. several plain radiographs of the spine, pelvis and hip joints, carried out after accidental trauma showed scoliosis and mild arthrosis. Two years later the symptoms had evolved to severe spastic tetraparesis, bladder and bowel dysfunction and sensibility deficits below the clavicle level. Magnetic resonance imaging of the spine (Fig. 3) and CT myelogra-phy (Fig. 4) showed arachnoiditis at midthoracic levels, no contrast agent passage above the T4 level and extensive intramedullary syrinx at cervical and thoracic levels. Given the patient’s massive neurological disability no surgical the-rapy was initially advised. In the following year the patient, now aged 74, developed pain attacks in the lower limbs and a new MrI of the spine showed increased extension of the syrinx down to the conus medullaris. The patient underwent surgical exploration. Laminectomy at levels T7–T9 revealed dense arachnoid adhesions and the spinal cord was dilated and extremely atrophic. Intradural adherences were removed as much as possible and a James lumbar peritoneal shunt sys-tem was inserted communicating the intramedullary syrinx

Fig. 1 Magnetic resonance imaging of the spine showing arachnoiditis and syringomyelia at thoracic levels: T1-weighted (a) and T2-weight-ed (b) images in the sagittal plane and axial T2-weighted image at the level of vertebra T5 (c). The single arrow (a, b) points to an ex-pansive subarachnoid cyst located ventral to the spinal cord at levels T3–T5. Just caudal to the extramedullary cyst the spinal cord is tethe-red against the ventral contour of the dural sac and more caudally it is

enlarged and contains a fluid-filled cavity (syrinx) that extends from T5 down to the T11–T12 disc level (double arrow in a, b). on the axial image (c) the spinal cord is distorted and tethered ventrally. Following gadolinium administration no pathological enhancement was detected. residuals of the hemorrhage were not detected in the spinal canal by magnetic resonance imaging, however, T2* imaging was not done.

Fig. 2 post-operative T2-weighted magnetic resonance imaging of the spine in the sagittal plane. The single arrow (a) points to a shunt cat-heter placed into the subarachnoid cyst at the T4 level and the double arrow (b) points to the shunt catheter placed into the intramedullar syrinx cavity at T8

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171subarachnoid Hemorrhage-associated Arachnoiditis and syringomyelia

with the peritoneal cavity. post-operatively the neurological deficits were unchanged and did not show any improvement in the follow-up (24 months). A post-operative MrI exami-nation (Fig. 5) showed a collapsed syrinx at cervical levels and extensive myelomalacia at thoracic and conus levels.

Discussion

The two patients in this communication did not have any anamnesis of spinal disease, meningitis, trauma or any other

known etiology for arachnoiditis and syringomyelia prior to sAH. Thus, no spinal imaging showing normal spinal ana-tomy was done preceding sAH. Conversely, there is no rea-son to believe that in these patients another etiology other than sAH would be responsible and in both cases there was no pathological process at the foramen magnum.

spinal adhesive arachnoiditis can be caused by various pathological processes with the common denominator of an inflammatory process leading to fibrosis of the arach-noid. Development of blockage of the cerebrospinal fluid (CSF) flow and arachnoid cysts can be associated. Known

Fig. 3a–c T2-weighted magnetic resonance sagittal images of the spine showing the whole extent of the syringomyelia from the upper cervical level down to the conus medullaris. The patient presented with scoliosis in the thoracic spine. Following gadolinium administration no pathological enhancement was detected. no signs of residual hemorrhage were identified in the spinal canal. Note absence of block at the foramen magnum

Fig. 4a–c sagittal reconstructi-ons of the computed tomography scan of the spine after intrathecal lumbar injection of contrast agent. At midthoracic levels the spinal cord has an irregular contour, is tethered dorsally and enlarged cranially and caudally. The syrinx does not communicate with the subarachnoid space. There is no contrast agent passage above the T4 level

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etiologies are purulent meningitis, tuberculosis, trauma, pre-vious spinal surgery, intervertebral disc herniation, spinal anesthetics and radiological contrast agents. subarachnoid hemorrhage has been identified as the cause of spinal arach-noiditis in a few cases [1–3]. post-sAH arachnoiditis most often affects the thoracic spine and the ruptured aneurysm causing the sAH is more commonly located in the poste-rior fossa [3]. Arachnoiditis following non-aneurysmal, perimesencephalic sAH has been reported in at least one case [4]. Factors which have been shown to contribute to the inflammatory response in post-SAH arachnoiditis act at the local level (sensory nerve neuropeptides, hemoglobin from lysed erythrocytes, prostaglandins, leukotriens, endothelin-1, serotonin, histamine, bradykinin, complement, thombin, activated platelets, pro-inflammatory cytokines, nitric oxide and free radicals) as well as systemically [5–8].

non-traumatic arachnoiditis can cause syringomyelia of the non-communicating type [1, 9]. It has been hypothesi-zed that vascular factors and altered CSF flow dynamics interact in this process [9]. The inflammatory reaction and scarring inherent in arachnoiditis lead to blockage of the spinal subarachnoid space and tethering of the spinal cord. This process also obliterates the spinal cord vasculature causing ischemia and small cavities of myelomalacia which later enlarge and coalesce due to fluid leakage into the spi-nal cord parenchyma, leading to the development of syring-omyelia. The precise role of CSF dynamics in fluid leakage and syrinx formation has been a matter of discussion. Under normal conditions CSF flow is synchronized with the car-diac cycle up (in diastole) and down (in systole) along the spinal canal. Intracranial and intraspinal CsF pressures

are normally in balance such that maneuvers which raise intrathoracic and intra-abdominal pressure (e.g. coughing, straining or erect posture) expand the intraspinal blood compartment and displace CsF from the intraspinal to the intracranial compartment. The CsF returns to the intraspinal compartment when the pressure goes down. An hypothesis proposed to explain syringomyelia formation is that in the presence of a spinal block a pressure raise inside the spinal canal will not be alleviated by CSF flow upstream in the levels caudal to the blockage site and the recurring pres-sure increases will induce fluid leakage into the spinal cord parenchyma [9]. This hypothesis is intuitively implausible as increased pressure on the outside of a fluid-filled cavity would not make the cavity expand but would rather result in compression. Another hypothesis is very similar to the gene-rally accepted hypothesis for development of hydromyelia in cases of CsF block at the foramen magnum: the pulsatile CsF pressure wave in systole is hindered as the spinal block produces a pressure drop in the caudal subarachnoid space at the same time that it is transmitted caudally inside the spinal cord through the central canal, leading to leakage of CsF from the central canal into the syrinx. This hypothesis has been simulated in a mathematical model [10]. A third hypothesis is the intramedullary pulse pressure theory [11] which suggests that in conditions of spinal block the systo-lic pulse pressure into the spinal cord increases in relation to the nearby subarachnoid space and presses extracellular fluid into the syrinx. In addition the role of deranged histod-ynamics [12] in syrinx formation has probably been under-rated. Under normal conditions the spinal cord, supported by its pial envelope, cranial and caudal attachments and by the dentate ligaments and dura mater, responds with a plas-tic adaptation of its length, curvature and cross-sectional area to alterations in the length and curvature of the spinal canal during movements of the body [12]. The importance of increased segmental mechanical strain on the spinal cord due to arachnoiditis-related tethering on syrinx development and progress has not been fully investigated.

syringomyelia has been treated by different surgical techniques including shunting of the syrinx (syringo-sub-arachnoid, syringo-peritoneal or syringo-pleural shunts), dissection of subarachnoid adhesions and decompression of the subarachnoid space with a fascia lata graft [1, 2]. The purpose of surgery is to stabilize the patient’s neurological status and the results vary with the pre-operative severity of arachnoid scarring as well as with the surgical techni-que. shunting is effective in relieving the syrinx pressure on the spinal cord tissue but has a limited effect on long-term outcome with recurrence rates ranging from recurrence in virtually all patients [1] to 60% [2]. This result is far from surprising as shunting does not treat the initial cause of syrinx formation but just alleviates the symptoms. Micro-

Fig. 5a, b post-operative follow-up T2-weighted sagittal Mr image of the spine: the syrinx is diminished in size at the cervical level with extensive myelomalacia at lower levels

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173subarachnoid Hemorrhage-associated Arachnoiditis and syringomyelia

surgical dissection of adhesions and decompression of the subarachnoid space has had better results, especially in patients where the adhesions were not extensive: in a repre-sentative surgical series stabilization of pre-operative neu-rological deficits was obtained in 83% of patients with focal subarachnoid scar but in only 17% when the scar extended over multiple levels or after previous surgery [1] and the overall recurrence rate was 33% in another series [2].

Conclusions

subarachnoid hemorrhage can cause spinal arachnoiditis and syringomyelia in patients several years after the ini-tial bleeding. As this condition is uncommon the diagnosis can be delayed, in some cases for years. syringomyelia is a devastating condition which causes immense suffering to patients and great frustration to physicians. Initially the patients present with vague neurological symptoms which have little correlation in onset and clinical manifestation with the underlying sAH. surgical intervention can pre-vent further progression of the neurological symptoms but no treatment has been found to reverse the process to any great extent. Thus it is important to increase awareness of post-sAH syringomyelia such that physicians will consider this diagnosis sooner, thereby allowing prompt radiological confirmation and surgical treatment.

Conflict of Interest The authors declare that there are no actual or potential conflicts of interest in relation to this article.

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