A unifying hypothesis for a patient with superficial siderosis, low-pressure headache, intraspinal cyst, back pain, and prominent vascularity

Case report

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A source of bleeding is often not evident during the evaluation of patients with superficial siderosis of the CNS despite extensive imaging. An intraspinal fluid-filled collection of variable dimensions is frequently observed on spine MR imaging in patients with idiopathic superficial siderosis. A similar finding has also been reported in patients with idiopathic intracranial hypotension. The authors report on a patient with superficial siderosis and a longitudinally extensive intraspinal fluid-filled collection secondary to a dural tear. The patient had a history of low-pressure headaches. His spine MR imaging and spine CT suggested the possibility of an underlying vascular malformation, but none was found on angiography. Repair of the dural tear resulted in resolution of the intraspinal fluid collection and CSF abnormalities. The significance of the association between superficial siderosis and idiopathic intracranial hypotension, and potential therapeutic and pathophysiological implications, are the subject of this report.

Abstract

A source of bleeding is often not evident during the evaluation of patients with superficial siderosis of the CNS despite extensive imaging. An intraspinal fluid-filled collection of variable dimensions is frequently observed on spine MR imaging in patients with idiopathic superficial siderosis. A similar finding has also been reported in patients with idiopathic intracranial hypotension. The authors report on a patient with superficial siderosis and a longitudinally extensive intraspinal fluid-filled collection secondary to a dural tear. The patient had a history of low-pressure headaches. His spine MR imaging and spine CT suggested the possibility of an underlying vascular malformation, but none was found on angiography. Repair of the dural tear resulted in resolution of the intraspinal fluid collection and CSF abnormalities. The significance of the association between superficial siderosis and idiopathic intracranial hypotension, and potential therapeutic and pathophysiological implications, are the subject of this report.

Superficial siderosis of the CNS results from hemosiderin deposition in the subpial layers of the brain and spinal cord.3,8–10 The hemosiderin deposition is a consequence of recurrent and persistent bleeding into the subarachnoid space. The classic clinical presentation of superficial siderosis includes adult-onset slowly progressive gait ataxia and less commonly appendicular ataxia, ataxic dysarthria, and sensorineural hearing impairment. The bleeding source may be not be detected despite extensive neuroimaging. Commonly performed investigations during the workup of superficial siderosis include MR imaging of the brain and spine, CT myelography, MR angiography, and cerebrospinal angiography. A prior history of trauma (at times trivial) or intradural surgery (commonly involving the posterior fossa) may be present.2,10 Often decades elapse between the presumed inciting event and the development of symptoms attributable to superficial siderosis.

In recent years an extraarachnoid, longitudinally extensive, intraspinal fluid-filled collection has been frequently noted in patients with superficial siderosis.6–13,21 A CT myelogram, dynamic CT myelogram, or digital substraction myelogram can identify a dural defect that connects the intrathecal space with the fluid-filled collection.6–8,11–13 The precise mechanism of bleeding in these cases is unknown. Limited experience suggests that repair of the defect may be associated with clinical stability or improvement, resolution of the intraspinal fluid-filled collection, and resolution of CSF evidence of subarachnoid bleeding.7,10–12,21

Some reports have also noted an association between superficial siderosis and either CSF hypovolemia or low-pressure headache.6,11,13 Cerebrospinal fluid hypovolemia is often a consequence of occult CSF leak, very frequently spontaneous, and typically within the spine rather than the skull base. It is a disorder that is frequently associated with dural defects, occasionally with intraspinal fluid collection of variable longitudinal extent, and not uncommonly with red blood cells or xanthochromia in the CSF.14,15,18,19 The cause of intracranial pachymeningeal enhancement in craniospinal hypotension is believed to be vascular dilation within the dura mater rather than meningeal inflammation.4,5,17 A similar pachymeningeal enhancement may also be observed in superficial siderosis.11,13

We report on a patient with superficial siderosis and back pain who had a longitudinally extensive intraspinal fluid collection due to a dural tear, in whom repair of the dural tear resulted in resolution of the intraspinal fluid collection, CSF xanthochromia, and back pain. This patient also had a history of orthostatic headache. His initial neuroimaging findings raised the question of an underlying vascular malformation but none was found on conventional myelography. The insights that these observations provide into the pathophysiology and workup of patients with superficial siderosis is discussed.

Case Report

History and Presentation

This 54-year-old man was evaluated for a 5-year history of slurred speech and a 2-year history of unsteady gait and decreased hearing. The onset of these symptoms was gradual and the course was slowly progressive. His symptoms review was also remarkable for a 1-year history of increased urinary frequency, decreased sense of smell, and low-back pain. The back pain was moderately severe and was unaccompanied by any radicular component. His medical history was notable for a major motor vehicle accident he experienced at age 34. Twenty years prior he had experienced orthostatic headaches that spontaneously resolved in 2 years. Seven years prior he started experiencing complex partial seizures that were well controlled with valproate and these did not recur despite discontinuation of the medication 4 years earlier. His examination showed bilateral decreased hearing, an ataxic dysarthria, and irregularity of rapid alternating movements with the hands and feet. His deep tendon reflexes were brisk and the plantar response was flexor. He had a wide-based ataxic gait and was unable to walk on his toes and heel, or tandem.

Cerebrospinal fluid analysis revealed 1243 red blood cells/μl without an increase in the white blood cell count. Xanthochromia was present, CSF glucose was normal, and CSF protein was elevated to 95 mg/dl. The opening pressure was normal at 175 mm water. Brain MR imaging showed severe cerebellar (hemispheric and vermian) and brainstem atrophy (Fig. 1A) with the characteristic superficial siderosis-related T2 hypointensity around the cerebellum and brainstem (Fig. 1B) and along the supratentorial fissures (Fig. 1C). The hypointensity was striking on gradient echo sequences (Fig. 1C). Spine MR imaging showed a linear T2 hypointensity along the cervical and thoracic cord consistent with hemosiderin deposition. Also present was a fluid-filled collection in the anterior spinal canal from C-2 to T-7 (Fig. 1D and E). Abnormal pial vascularity was noted on contrast-enhanced MR imaging of the cervical spine (Fig. 1F). A CT myelogram showed abnormal extradural accumulation of contrast material ventrally between C-4 and T-8; the contrast material accumulation was largest between T-3 and T-5 (Fig. 2A). The findings were worrisome for a CSF leak but the precise location of the leak could not be determined from this study. An abnormally dilated pial venous plexus was noted to extend from the foramen magnum to C-7 (Fig. 2B). A digital substraction myelogram suggested a CSF leak at the T-4 level (Fig. 2C). A dynamic CT myelogram confirmed an anterior leak, slightly to the left of the midline at the T-3 level (Fig. 2D and E). The examination was performed in the head down position and the leak was noted to fill the anterior epidural space superiorly, but not inferiorly. Old compression fractures, likely related to prior trauma, were noted at T-3 (Fig. 2D), T-9, T-11, and L-1 vertebral bodies on all MR imaging and CT studies. The prominent pial vascularity noted on the contrast-enhanced cervical spine MR imaging and the evidence of a dilated and tortuous pial venous plexus noted on the CT myelogram were considered suspicious for an arteriovenous fistula. No evidence of an aneurysm or arteriovenous malformation was noted on a cerebrospinal angiogram.

Fig. 1.
Fig. 1.

Preoperative MR images. A: Sagittal T1-weighted brain image showing severe cerebellar (arrow) and brainstem (dotted arrow) atrophy. B: Axial T2-weighted image showing the characteristic T2 hypointensity due to hemosiderin deposition along the cerebellum (arrows) and around the brainstem (black dotted arrow). C: Axial gradient echo image demonstrating the T2 hypointensity along the sylvian (arrows) and interhemispheric (dotted arrows) fissures and along the perimesencephalic cistern (circle). D: Sagittal and axial (inset) T2-weighted images of the cervical spine showing a longitudinally extensive anterior intraspinal fluid collection (arrows). E: Sagittal and axial (inset) T2-weighted images of the thoracic spine demonstrating extension of the anterior intraspinal fluid-filled collection to the lower thoracic levels (arrows). F: Sagittal T2-weighted image of the cervical spine with contrast enhancement showing prominent anterior and posterior leptomeningeal enhancement (arrows) possibly due to prominent pial vascularity.

Fig. 2.
Fig. 2.

Preoperative (A–E) and postoperative (F–H) images. A: Axial slice from a CT myelogram showing accumulation of extradural contrast material at T-4 (arrow). B: Coronal reformatted image from a CT myelogram showing a prominent and tortuous vessel (arrows); the possibility of an underlying vascular malformation was not substantiated on an angiogram. C: Digital substraction myelogram identifying the site of leak around T-4 (arrow); note the thicker column above T-4 due to leakage of the contrast material into the anterior fluid-filled collection. D: Reformatted sagittal image from a dynamic CT myelogram shows leakage of the contrast dye at T-3 (arrow). Also noted is the collapsed T-3 vertebral body (asterisk). E: Axial CT myelogram at T-3 shows that the dye leak is to the left of the midline (arrow). F and G: Sagittal and axial (inset) T2-weighted cervical (F) and thoracic (G) MR images showing resolution of the anterior intraspinal fluid-filled collection after repair of the T-3 dural tear (4 months after surgery). H: Sagittal fat-saturated postcontrast T1-weighted MR image demonstrating resolution of the pial vascularity anterior and posterior to the cord.

Operation and Postoperative Course

A T2–4 laminectomy exposed a well-developed cyst wall in the anterior epidural space. Brisk CSF flow was noted medial to the left T-3 nerve root, which was sacrificed and divided. Through a posterolateral durotomy, the dentate ligament was also sectioned to allow rotation and elevation of the spinal cord. With the aid of the operating microscope, an 8-mm vertical dural tear was identified anteriorly near the midline. This tear was repaired using small sutures. No abnormal vascularity or focal hemosiderin staining was noted in the region of the dural tear or spinal cord.

At 4-months follow-up the patient noted no worsening of symptoms and his neurological examination results were unchanged. He did note that immediately after the operation he had complete resolution of his back pain. A cervical and thoracic spine MR imaging examination performed at follow-up showed interval resolution of the anterior epidural cervical spine fluid collection (Fig. 2F and G) and pial vascularity (Fig. 2H). Evidence of T2–4 laminectomy and posterior paraspinal and epidural postoperative fluid collection was present. The low signal deposition along the cervical and thoracic cord was less prominent than the preoperative scans. A repeat lumbar puncture showed resolution of the xanthochromia and decrease in the CSF red blood cell count to 161/μl. Cerebrospinal fluid protein was elevated to 82 mg/dl.

Discussion

Superficial siderosis is a very slowly progressive disorder. A prior history of trauma or intradural surgery is commonly present. It is possible that in our patient a traumatic tear developed in the anterior dura at T-3 due to his motor vehicle accident 2 decades earlier that caused a CSF leak and made his body predisposed to the slow bleeding into the CSF. Spontaneous resolution of orthostatic headaches can occur in CSF hypovolemia, either through spontaneous sealing or considerable slowing down of the leak.15,16 Our patient's history of orthostatic headache was likely due to CSF hypovolemia. Given the short follow-up duration and long natural history of the disease we cannot say that the dural tear repair was successful in arresting progression. The surgical repair of the dural tear was accompanied by a prompt, complete, and enduring resolution of the back pain. Back pain has been rarely reported in superficial siderosis.3,20 In 1 case it was the predominant symptom.20 Back pain is also a known accompaniment of spontaneous intraspinal CSF leak. Also, the pain could have been secondary to the large intraspinal, extradural CSF-filled cyst.

Not infrequently, angiography is included in the workup of patients with superficial siderosis in an attempt to search for a vascular malformation as a potential source of bleeding. In our patient the pial vascularity noted on contrast-enhanced cervical spine MR imaging (Fig. 1F) and indication on the CT scan of a tortuous and dilated pial plexus (Fig. 2B) suggested an underlying vascular malformation, but none was found on cerebrospinal angiography. It has been suggested that pial siderosis may contribute to sclerosis of the epidural plexus of veins, leading to venous hypertension that may manifest as prominent pial vascularity on contrast-enhanced MR imaging.21 Imaging evidence of engorgement of intradural and epidural veins may also be observed with CSF hypovolemia.1,15 The resolution of pial vascularity after repair of the dural defect suggests that this finding was related to CSF hypovolemia. The more recently reported association between superficial siderosis and CSF hypovolemia has raised the speculation that the increased CSF erythrocytes in superficial siderosis could be related to intradural vascular engorgement that accompanies CSF hypotension.11 Awareness of these associations in superficial siderosis is important because it may obviate the need for angiography in some cases.

There are a number of similarities between the syndrome of craniospinal hypovolemia and those patients with superficial siderosis who have an intraspinal fluid-filled collection: both may have a history of orthostatic headache, and imbalance and back pain may be noted in either condition. Both conditions may be accompanied by dural tears and be associated with intraspinal cysts or dural diverticula. Increased red blood cells in the CSF may be observed in either condition; a prior history of intradural surgery or trauma (at times trivial) is a risk factor for both, and both conditions may have imaging evidence of vascular engorgement or pachymeningeal enhancement.6,11,13–15,18,19 Whereas recurrent and persisting bleeding into the CSF is a defining characteristic of superficial siderosis, the presence of many red blood cells and xanthochromia in the CSF is relatively rare in craniospinal hypovolemia. Our patient had overlapping features of these disorders. The associations common to craniospinal hypovolemia and superficial siderosis may provide further insights into the mechanism of bleeding in patients with superficial siderosis who have an intraspinal fluid-filled collection.

Disclaimer

The authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this paper.

References

Article Information

Address correspondence to: Neeraj Kumar, M.D., Department of Neurology, Mayo Clinic, 200 First Street SW, Rochester, Minnesota 55905. email: kumar.neeraj@mayo.edu.

Please include this information when citing this paper: published online November 6, 2009; DOI: 10.3171/2009.10.JNS091125.

© AANS, except where prohibited by US copyright law.

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Figures

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    Preoperative MR images. A: Sagittal T1-weighted brain image showing severe cerebellar (arrow) and brainstem (dotted arrow) atrophy. B: Axial T2-weighted image showing the characteristic T2 hypointensity due to hemosiderin deposition along the cerebellum (arrows) and around the brainstem (black dotted arrow). C: Axial gradient echo image demonstrating the T2 hypointensity along the sylvian (arrows) and interhemispheric (dotted arrows) fissures and along the perimesencephalic cistern (circle). D: Sagittal and axial (inset) T2-weighted images of the cervical spine showing a longitudinally extensive anterior intraspinal fluid collection (arrows). E: Sagittal and axial (inset) T2-weighted images of the thoracic spine demonstrating extension of the anterior intraspinal fluid-filled collection to the lower thoracic levels (arrows). F: Sagittal T2-weighted image of the cervical spine with contrast enhancement showing prominent anterior and posterior leptomeningeal enhancement (arrows) possibly due to prominent pial vascularity.

  • View in gallery

    Preoperative (A–E) and postoperative (F–H) images. A: Axial slice from a CT myelogram showing accumulation of extradural contrast material at T-4 (arrow). B: Coronal reformatted image from a CT myelogram showing a prominent and tortuous vessel (arrows); the possibility of an underlying vascular malformation was not substantiated on an angiogram. C: Digital substraction myelogram identifying the site of leak around T-4 (arrow); note the thicker column above T-4 due to leakage of the contrast material into the anterior fluid-filled collection. D: Reformatted sagittal image from a dynamic CT myelogram shows leakage of the contrast dye at T-3 (arrow). Also noted is the collapsed T-3 vertebral body (asterisk). E: Axial CT myelogram at T-3 shows that the dye leak is to the left of the midline (arrow). F and G: Sagittal and axial (inset) T2-weighted cervical (F) and thoracic (G) MR images showing resolution of the anterior intraspinal fluid-filled collection after repair of the T-3 dural tear (4 months after surgery). H: Sagittal fat-saturated postcontrast T1-weighted MR image demonstrating resolution of the pial vascularity anterior and posterior to the cord.

References

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