Experimental superficial siderosis of the central nervous system: biochemical correlates

Frequency, Extent, and Correlates of Superficial Siderosis and Ependymal Siderosis in Premature Infants with Germinal Matrix Hemorrhage: An SWI Study

BACKGROUND AND PURPOSE

Germinal matrix intraventricular hemorrhage is a common complication of prematurity. An underrecognized complication of germinal matrix intraventricular hemorrhage is superficial siderosis, and the clinical consequences of superficial siderosis are not well-known. We aimed to investigate the prevalence, anatomic distribution, and severity of superficial siderosis and ependymal siderosis in premature infants with germinal matrix intraventricular hemorrhage using SWI.

MATERIALS AND METHODS

In this retrospective study, we included 88 patients across all grades of germinal matrix intraventricular hemorrhage who underwent MR imaging at term-equivalent age. Images were evaluated for the presence, distribution, and severity of superficial siderosis and ependymal siderosis. Univariate and multivariate logistic regression analyses were performed to determine factors associated with superficial siderosis and ependymal siderosis. The agreement among T1, T2, and SWI sequences was examined.

RESULTS

Seventy-two patients had brain stem superficial siderosis, and 79 patients had ependymal siderosis. The presence, extent, and severity of superficial siderosis and ependymal siderosis were closely related to the grade of germinal matrix intraventricular hemorrhage and intraventricular hematoma volume. Brain stem superficial siderosis had a stronger correlation with intraventricular hemorrhage than with cerebellar hemorrhage. Compared with SWI, T1 and T2 sequences detected only small proportions of patients with superficial siderosis (12.5% and 6.9%, respectively).

CONCLUSIONS

The incidence of superficial siderosis and ependymal siderosis is very high in preterm infants with germinal matrix intraventricular hemorrhage when assessed by SWI at term-equivalent age. The presence and extent of superficial siderosis and ependymal siderosis are closely related to germinal matrix intraventricular hemorrhage grade and intraventricular hematoma volume. Additional prospective studies using SWI are needed to clearly determine the clinical consequences of germinal matrix intraventricular hemorrhage with superficial siderosis and ependymal siderosis.

Superficial Siderosis of the Central Nervous System: Neurotological Findings Related to Magnetic Resonance Imaging

OBJECTIVE

To compare the neurotological results of five patients suffering from progressive hearing loss and ataxia due to superficial siderosis (SS) with the magnetic resonance imaging (MRI) findings.

STUDY DESIGN

Retrospective case review.

SETTING

Primary and hospital care center.

PARTICIPANTS

Five adult patients with neurotological symptoms of SS underwent MRI with acquisition of our temporal bone protocol including 3D-constructive interference in steady state (3D-CISS) and susceptibility-weighted imaging (SWI). All patients underwent a complete neurotological examination, the results of which were compared with the imaging findings.

MAIN OUTCOME MEASURES

Cochleovestibular deficits were present in all five patients as determined by uni- or bilateral bithermal caloric testing and/or video head impulse tests. Sacculocollic reflex was present with increased P1 and N1 latencies on both sides in all patients. MRI revealed an extensive hypointense SWI signal outlining the surface of the brain and the VIIIth cranial nerve in all five patients. Desynchronization of the brainstem auditory evoked potentials (BAEP) and partial or complete absence of the visual suppression of vestibulo-ocular reflex during the pendular rotatory test was particularly consistent with the lesions of the cochleovestibular nerves as well as the cerebellar atrophy seen on MRI.

CONCLUSION

The MRI results with SWI were related to neurotological findings in patients suffering from sensorineural deafness with ataxia due to SS. Our findings support the integration of the SWI and 3D-CISS sequences into the MRI protocol for all patients referred for evaluation of the extent of SS.

Isolated spinal cord compression syndrome revealing delayed extensive superficial siderosis of the central nervous system secondary to cervical root avulsion

CONTEXT

Cervical root avulsion secondary to traumatic plexus injury is a rare etiology of superficial siderosis (SS) of the central nervous system (CNS). We describe the case of an isolated progressive compressive myelopathy revealing this complication and discuss the pathogenesis of such a presentation, its clinical and imaging peculiarities with a literature review.

FINDINGS

We report on the case of a 48-year-old man with history of left brachial plexus injury at the age of 2 years. Since the age of 38 years, he had presented with a progressive paraplegia, bladder and erectile dysfunction, neuropathic pain and sensory level. The diagnosis was made by spinal cord and brain magnetic resonance follow-up imaging revealing hypointensity T2-weighted gradient echo linear dark rim around the entire neuraxis and cervical dural pseudomeningoceles. These MRI findings were suggestive of extensive hemosiderin deposition consolidating the diagnosis of SS of CNS.

CONCLUSION/CLINICAL RELEVANCE

Our case report illustrates diagnosis difficulties in unusual or paucisymptomatic presentations of SS. A history of brachial plexus trauma with nerve root avulsion should prompt gradient-echo T2-weighted imaging to bring out such a complication. Superficial siderosis of the CNS should be included in the panel of differential diagnosis of the parethospastic syndromes and compressive myelopathy.

Bilateral Vestibulopathy in Superficial Siderosis

Background: Superficial siderosis (SS) is a rare condition in which hemosiderin, an iron storage complex, is deposited in neural tissues because of recurrent subarachnoid bleeding. Hemosiderin deposition in the vestibulocochlear nerve (CN VIII), brain, spinal cord and peripheral nerve can cause sensorineural hearing loss (SNHL) and postural imbalance, but much remains unknown about the vestibular manifestations of SS.

Objectives: To report the clinical course, cochleovestibular status, and patterns of vestibulopathy during follow-up of a relatively large case series, and to discuss the possible pathophysiological mechanism of vestibular deterioration.

Methods: Six patients diagnosed with SS by magnetic resonance imaging (MRI) were enrolled. Their medical records and radiological findings were retrospectively reviewed, particularly in terms of progression of the vestibulocochlear manifestations and the radiological characteristics.

Results: All six patients had SNHL. Five of them exhibited progressive hearing loss over years, which was asymmetric in four. On their most recent evaluations, patients showed cerebellar ataxia with combined central and peripheral vestibulopathy on both sides (n = 4), a bilateral peripheral vestibulopathy (n = 1) or isolated central vestibulopathy (n = 1). Notably, the former four patients showed an evolution of isolated central vestibulopathy into combined central and peripheral vestibulopathy. Hypo-intense lesions on T2 weighted MRIs were evident around the cerebellum in all patients, but such lesions were observed around the brainstem in five and the CN VIII in four. The cochlea-vestibular dysfunction generally progressed asymmetrically, but no left-right asymmetry was evident on MRI.

Conclusions: SS typically presents as bilaterally asymmetric, progressive cochleovestibular dysfunction with cerebellar ataxia. The pattern of vestibular dysfunction is usually combined central and peripheral vestibulopathy on both sides. Thus, precise identification of audiovestibular dysfunction and central signs is essential in SS, and patients with SS should undergo regular, comprehensive neurotological evaluation to optimize their treatments and prognosis.

High resolution magnetic resonance imaging for exposing facial nerve zonal vulnerability to microbleeds: A rare cause of facial palsy

Background We report a case of hypertensive microbleeds strategically located at the attached segment (AS) and root entry zone (REZ) at the left facial nerve causing facial paralysis. Case Report A 60-year-old woman presented with sudden onset left facial paralysis. Medical history was significant for poorly controlled hypertension secondary to bilateral adrenal hyperplasia (primary hyperaldosteronism). The patient was initially treated for presumptive Bell's palsy. Subsequent magnetic resonance imaging of the brain and internal auditory canal showed two microbleeds at the left cerebellopontine angle. Dedicated coronal T1 magnetization prepared rapid acquisition gradient echo and T2 sampling perfection with application optimized contrasts using different flip angle evolution sequences revealed two acute microbleeds located at the attached AS and REZ of the left facial nerve. The patient experienced only partial recovery from House-Brackmann grade IV facial paralysis at presentation to a House-Brackmann grade III facial paralysis at 1 year of follow up. Conclusions To the best of the authors' knowledge, this is the first reported case of facial paralysis caused by microbleeds directly affecting the vulnerable AS and REZ facial nerve segments. We discuss the zonal microanatomy of the facial nerve and the crucial role of high resolution MRI for diagnosis.

Cochlear implantation is a therapeutic option for superficial siderosis patients with sensorineural hearing loss

Background:

Superficial siderosis is a rare disease that results from chronic bleeding in the subarachnoid space. Haemosiderin deposits throughout the subpial layers of the brain and spinal cord lead to progressive sensorineural hearing loss, which is seen in 95 per cent of patients with superficial siderosis. The impact of cochlear implantation on the quality of life of superficial siderosis patients is under debate.

Case report:

A 38-year-old male with superficial siderosis presented with bilateral progressive sensorineural hearing loss. The patient underwent cochlear implantation and his quality of life was improved as evaluated by the Abbreviated Profile of Hearing Aid Benefit inventory.

Conclusion:

The remarkable improvement in Abbreviated Profile of Hearing Aid Benefit scores shown in this study indicates that cochlear implantation leads to a better quality of life in superficial siderosis patients.

Agranulocytosis with deferiprone treatment of superficial siderosis

Superficial siderosis of the central nervous system is a rare neurological disorder caused by deposits of haemosiderin on subplial brain matter. Characterised by a thin dark layer surrounding the brain stem, cerebellum and cortical fissures on the T2-weighted MRI, symptoms include sensorineural hearing loss and progressive gait ataxia. A specific aetiology for the blood in the subarachnoid space is identified in less than 50% of cases. While identification of a specific vascular defect allows for vascular repair, treatment options are limited for idiopathic superficial siderosis. Recently, a pilot safety study demonstrated promising results using an iron chelator, deferiprone. While this approach is promising, we present a potential serious complication of this therapy-the first report of agranulocytosis in the treatment of superficial siderosis following deferiprone therapy.

Vestibular function in superficial siderosis

BACKGROUND

Superficial siderosis (SS) is caused by repeated or continuous bleeding into the subarachnoid space that results in iron from hemoglobin (hemosiderin) being deposited on the surface of the brain. Clinically, the condition is characterized by sensorineural deafness, ataxia, and pyramidal signs. However the mechanism of peripheral vestibular disturbance was not revealed. We show the vestibular function of SS patients, and shed light on saccule-inferior vestibular nerve.

METHODS

Over the past 9 years, 5 patients were definitively diagnosed with SS by MRI in our department. These patients were subjected to balance testing.

RESULTS

Vestibular evoked myogenic potential (VEMP) was observed in patients who had suffered from SS for a short period but tended to be diminished or absent in patients who had suffered from the condition for a longer period.

CONCLUSIONS

These findings in SS patients suggest that saccule-inferior vestibular function is maintained at early stages of the disorder. Our study may help to clarify the mechanism of SS.

Temporal bone histopathology in a case of sensorineural hearing loss caused by superficial siderosis of the central nervous system and treated by cochlear implantation

OBJECTIVE

To evaluate the histopathology of the temporal bones of a patient with documented superficial siderosis of the central nervous system who underwent right cochlear implantation six years before death.

BACKGROUND

Superficial siderosis of the central nervous system is due to chronic or repeated subarachnoid hemorrhage and results in sensorineural deafness in 95% of affected individuals in addition to other neurologic findings. The deposition of hemosiderin in the meninges and around cranial nerves is thought to be causative. There have been no previous reports of temporal bone pathology in this disorder.This 57 year old man developed progressive, bilateral hearing loss starting in his 30's with loss of pure tone thresholds and word recognition. He underwent a right cochlear implant at age 51 with full insertion of the device.

METHODS

The temporal bones and brainstem were fixed in formalin and prepared for histologic study by standard techniques. Special stains, including Gomori stain for iron were performed on sections of the temporal bones and cochlear nucleus.

RESULTS

There was severe bilateral degeneration of the organ of Corti, spiral ligament, stria vascularis, and spiral ganglion cells. Gomori stain revealed iron deposits within the spiral ligament, stria vascularis and in the subepithelial mesenchymal tissue of the maculae of the vestibular system. Evaluation of the cochlear nucleus revealed iron deposits within glial cells and larger cells, probably macrophages, near the CSF surface. On the right side, the track created by the cochlear implant entered the scala tympani and continued to mm17, as measured from the round window.

DISCUSSION AND CONCLUSION

This is the first known case of superficial siderosis with documented temporal bone histopathology. Hearing loss was likely caused by severe degeneration of spiral ganglion cells in both ears, despite the presence of remaining hair cells in the middle and apical turns. This was consistent with cochlear neuronal degeneration and retrograde degeneration of spiral ganglion cells within the inner ear, or alternatively, consistent with primary degeneration of hair cells and neural structures within the cochlea. Despite the presence of neural degeneration, the patient achieved a word recognition score of 28% six months following implantation.

Superficial siderosis of the CNS and otoneurological manifestations

Superficial siderosis is an uncommon condition occurring in central nervous system (CNS) due to deposition of hemosiderin in the subpial meningeal layer causing progressive neurological dysfunction. The classical clinical manifestation is a triad of chronic ataxia, bipyramidal signs and progressive bilateral symmetrical sensorineural hearing loss (SNHL). It has rarely been reported in Indian literature. We report an unusual case of superficial siderosis in a 60-year-old farmer who presented with the above triad along with involvement of olfactory nerve. We present this case to highlight the fact that progressive SNHL can be an important sign for the early awareness of this rare disorder. The literature on superficial siderosis is reviewed and the pathogenesis is discussed.

Superficial siderosis - mechanism of disease: an alternative hypothesis

Superficial siderosis is an increasingly common diagnosis due to advances in imaging. Resulting from the presence of blood in the subarachnoid space, it leads to progressively debilitating ataxia, deafness and myelopathy. Magnetic resonance imaging has revolutionized diagnosis and management of this condition. In one-third of patients with this diagnosis, no subarachnoid bleed can be identified. A lack of sensitivity in our ability to detect subarachnoid bleed is a possible explanation in this group of patients. A novel approach would be to consider defects in the body's defense against intracranial iron overload as a possible cause of this disease. A disproportionately few patients develop superficial siderosis compared with the number who develop subarachnoid bleed from various clinical conditions. Normal physiological protective mechanisms exist in the central nervous system to protect it from damage by blood, haeme or free iron. Deficiency and defect of these protective mechanisms can provide insight into the pathogenetic mechanism of the group of patients where no subarachnoid haemorrhage is identified.

Superficial siderosis mimicking amyotrophic lateral sclerosis

We report a case of superficial siderosis erroneously diagnosed as amyotrophic lateral sclerosis. The patient's symptoms began 18 years prior with unilateral upper extremity weakness, fasciculations, and hyperreflexia. The patient then developed ataxia and hearing loss 15 years after his original symptoms. The magnetic resonance images revealed superficial siderosis involving the spinal cord and brain. We want to attract attention to superficial siderosis as a rare amyotrophic lateral sclerosis mimic disorder.

Neuroimaging in superficial siderosis: an in-depth look

Despite extensive imaging, a source of bleeding is often not evident during the evaluation of patients with superficial siderosis (SS) of the central nervous system. An intraspinal fluid-filled collection of variable dimensions is frequently seen on spine MR imaging in patients with idiopathic SS. A similar finding has also been reported in patients with craniospinal hypotension. This review discusses the role of multitechnique imaging in the work-up of patients with SS and focuses on recent developments.

[Secondary superficial siderosis of the central nervous system: report of three cases]

BACKGROUND

Superficial siderosis (SS) is an under-recognized entity. It is due to repeated microhemorrhages in the subarachnoid spaces resulting in a deposit of hemosiderin at the surface of the central nervous system and/or the cranial nerves. The origin of microhemorrhages remains unknown in almost one third of cases and therefore no treatment can be recommended. Through a literature review and new observations, our goal is to detail the outcome of patients with a recognized etiology of SS and treated surgically.

METHODS

Series of three cases and review of the literature.

RESULTS

We present three patients with symptomatic SS for whom the origin of microhemorrhages was found. The first two patients complained of longstanding ataxia and neurosensory deafness while the third patient presented with urinary retention, vertigo, diplopia and facial paresis. Neuroradiological explorations revealed a left temporoparietal cavernoma, a fronto-orbital arterio-venous malformation and a cauda equina myxopapillary ependymoma respectively. Surgical resection of the source of hemorrhage was performed in all cases. All outcomes were good with improvement of their SS-related symptoms. These cases are discussed and the current literature is reviewed.

CONCLUSION

It is important to recognize SS since the treatment of the bleeding source may prevent further deterioration and may even in some cases improve the clinical condition.

The pathology of superficial siderosis of the central nervous system

Chronic or intermittent extravasations of blood into the subarachnoid space, and dissemination of heme by circulating cerebrospinal fluid, are the only established causes of superficial siderosis of the central nervous system (CNS). We studied the autopsy tissues of nine patients by iron histochemistry, immunocytochemistry, single- and double-label immunofluorescence, electron microscopy of ferritin, and high-definition X-ray fluorescence. In one case, frozen brain tissue was available for quantitative assay of total iron and ferritin. Siderotic tissues showed extensive deposits of iron and ferritin, and infiltration of the cerebellar cortex was especially severe. In addition to perivascular collections of hemosiderin-laden macrophages, affected tissues displayed iron-positive anuclear foamy structures in the neuropil that resembled axonal spheroids. They were especially abundant in eighth cranial nerves and spinal cord. Double-label immunofluorescence of the foamy structures showed co-localization of neurofilament protein and ferritin but comparable merged images of myelin-basic protein and ferritin, and ultrastructural visualization of ferritin, did not allow the conclusion that axonopathy was simply due to dilatation and rupture of fibers. Heme-oxygenase-1 (HO-1) immunoreactivity persisted in macrophages of siderotic cerebellar folia. Siderosis caused a large increase in total CNS iron but high-definition X-ray fluorescence of embedded tissue blocks excluded the accumulation of other metals. Holoferritin levels greatly exceeded the degree of iron accumulation. The susceptibility of the cerebellar cortex is likely due to Bergmann glia that serve as conduits for heme; and the abundance of microglia. Both cell types biosynthesize HO-1 and ferritin in response to heme. The eighth cranial nerves are susceptible because they consist of CNS axons, myelin, and neuroglial tissue along their subarachnoid course. The persistence of HO-1 protein implies continuous exposure of CNS to free heme or an excessively sensitive transcriptional response of the HO-1 gene. The conversion of heme iron to hemosiderin probably involves both translational and transcriptional activation of ferritin biosynthesis.

Superficial siderosis: a case report and review of the literature

BACKGROUND

A 48-year-old man with a past history of a car-accident-induced coma at the age of 3 years and spontaneous bilateral subdural hematomas at the age of 34 years presented with a 2-year history of worsening gait difficulties, clumsiness and dysarthria. CT scans of the brain taken during the 6 months leading up to his presentation had revealed chronic subarachnoid hemorrhage, but angiograms had not been able to identify the source of bleeding.

INVESTIGATIONS

Neurological examination, brain MRI scan, lumbar puncture, four-vessel cerebral angiogram and spinal angiogram.

DIAGNOSIS

Superficial siderosis; a complete review of the current literature on the condition is provided.

MANAGEMENT

Iron chelating agents.

Auditory manifestations of superficial hemosiderosis of the central nervous system

Superficial hemosiderosis of the central nervous system (SH-CNS) is a relatively rare condition caused by chronic or repeated subarachnoid bleeding. The aim of this article was to present hearing disorders related to SH-CNS, and to describe results of magnetic resonance imaging (MRI) to confirm the diagnosis. We performed a retrospective case review at a tertiary referral center. Clinical presentation, auditory manifestations and MRI findings of two patients with SH-CNS are reported. The two patients experienced bilateral sensorineural hearing loss (SNHL) that progressively worsened. MRI revealed typical aspects of SH-CNS on T2-weighted images. Progressive bilateral SNHL is the most common manifestation of SH-CNS. The otolaryngologist should be aware of this disease that can be easily diagnosed with MRI.

[Superficial siderosis of the CNS. 2 cases and a review of the literature]

Superficial siderosis of the CNS is a rare disease. The superficial deposition of haemosiderin in the cerebrum, cerebellum and spinal cord is due to chronic and recurrent subarachnoidal haemorrhage (SAH). Known sources of bleeding are vascular CNS-tumours, CSF-cavity lesions, vascular malformations, nerve root lesions and neurosurgical interventions. Detection of the source of bleeding is successful in only about 50% of cases. The clinical syndrome is characterized by sensorineural deafness, cerebellar ataxia and pyramidal signs. CSF-investigation might be indicative for SAH, while ferritin and ionic iron can be elevated in the CSF. CT is unspecific and insensitive but MR imaging of the brain and spinal cord is very sensitive and specific. The elimination of the source of bleeding alone might prevent the progression of the disease, therefore, an early and extensive search for this source is highly recommended.

Heme oxygenase in experimental intracerebral hemorrhage: the benefit of tin-mesoporphyrin

The prognosis of intracerebral hemorrhage (ICH) is unfavorable. Beyond immediate mass effect and tissue destruction, ICHs cause additional neuronal loss in a "perifocal reactive zone." Heme in ICH induces heme oxygenase-1 (HO-1), and the action of this enzyme on heme yields ferrous iron, biliverdin, and carbon monoxide. Iron is ultimately converted to ferritin and hemosiderin. Free iron is tissue-toxic, and inhibition of HO-1 should provide protection against additional damage. Experimental ICHs were made in adult rabbits by the stereotaxic injection of autologous blood, and the induction of HO-1 and increase in ferritin were followed by confocal immunofluorescence microscopy. Heme diffused rapidly through perivascular spaces, and HO-1 reaction product first occurred in perivascular cells and microglia. At this stage, HO-1 and ferritin showed extensive colocalization. As ICH resolution progressed, HO-1 immunoreactivity faded while ferritin and hemosiderin continued to accumulate. This process was accompanied by a gradient of destruction of neuronal cell bodies and dendrites in the perifocal reactive zone. In an effort to inhibit HO-1, repeated intravenous injections of tin-mesoporphyrin IX (SnMP) were given to ICH-bearing rabbits. The ICH disrupted the blood-brain barrier sufficiently to allow SnMP to enter the brain in pharmacological amounts, and the metalloporphyrin provided significant protection against neuronal loss.

Longitudinal Analysis of Hearing Loss in a Case of Hemosiderosis of the Central Nervous System

OBJECTIVE

To describe cochleovestibular aspects of superficial hemosiderosis of the central nervous system.

BACKGROUND

Superficial hemosiderosis of the central nervous system is a rare disease in which cochleovestibular impairment, cerebellar ataxia, and myelopathy are the most frequent signs. Chronic recurrent subarachnoidal hemorrhage with bleeding into the cerebrospinal fluid is the cause of deposition of hemosiderin in leptomeningeal and subpial tissue, cranial nerves, and spinal cord. Removing the cause of bleeding can prevent irreversible damage to these structures. Because this is the only effective treatment, an early diagnosis is crucial.

STUDY DESIGN

Retrospective case review.

SETTING

Tertiary referral center.

PATIENT

A 72-year-old woman with superficial hemosiderosis of the central nervous system that developed when she was age 39.

METHODS

Neurologic and imaging diagnostic examinations and longitudinal evaluation of cochleovestibular features were performed. Neurosurgery was not performed.

RESULTS

Progressive bilateral sensorineural hearing loss and severe vestibular hyporeflexia developed within 15 years, which can be attributed to lesions in the cochleovestibular system. Additional pathology of the central nervous system developed later.

CONCLUSION

The patient demonstrated cochlear and vestibular findings that are typical of this pathologic condition. It is the first documented case with extensive serial audiometry used to precisely outline the degree of hearing deterioration during the course of the disease.

Superficial siderosis of the central nervous system: pathogenetic heterogeneity and therapeutic approaches

OBJECTIVE

Superficial siderosis of the central nervous system (CNS) is a rare chronic progressive disorder caused by chronic subarachnoid hemorrhage. We present four patients with superficial siderosis of the CNS to describe the characteristic symptoms, and to discuss the pathogenetic heterogeneity and possible new therapeutic approaches.

RESULTS

The causes of chronic subarachnoid bleeding in superficial siderosis were different. In two patients surgical treatment of ependymoma or cerebral cavernomas were the underlying diseases. No cause was detected in one patient. For the first time, we present one patient with vasculitis of the central nervous system associated with systemic hemochromatosis in superficial siderosis. Therapeutic approaches included exstirpation of cavernomas as the source of chronic bleeding in one patient, immunosuppressive therapy and venupunctures in the patient with vasculitis and hemochromatosis, and symptomatic treatment with chelating agents and antioxidants. The patients remained clinically stable for the follow-up period of up to 2 years.

CONCLUSIONS

Our cases underline the pathogenetic heterogeneity of superficial siderosis and favor the early diagnosis for prompt initiation of therapy. Besides treatment of the underlying condition, antioxidants and radical scavengers may be effective in halting the progression of the disease.

Tin-protoporphyrin prevents experimental superficial siderosis in rabbits

Superficial siderosis of the human central nervous system is caused by small continuous or recurrent subarachnoid hemorrhages that lead to the destructive deposition of hemosiderin. The excessive tissue iron derives from heme that is oxidized in a rate-limiting step by the enzyme heme oxygenase (HO), and especially the inducible form, HO-1. We postulated that competitive inhibition of HO by tin-protoporphyrin IX (SnPP) could prevent experimental superficial siderosis. Since synthetic metalloporphyrins do not cross the blood-brain barrier, SnPP was delivered directly into the cisterna magna. Rabbits received weekly intracisternal injections of washed autologous red blood cells (RBC) over a period of 1 to 16 wk. In companion experiments, SnPP was added to the suspension of RBC, or SnPP was injected without RBC. All injections caused increased HO-1 immunoreactivity in the Bergmann glia of the cerebellar cortex and in superficial astrocytes of the piriform cortex. The injections of RBC or RBC with added SnPP also generated a vigorous microglial response. The metalloporphyrin entered the tissue in inhibitory amounts and greatly reduced the accumulation of histochemically detectable iron. It did not alter the microglial response. The observations allowed the conclusion that SnPP suppressed heme oxidation but did not affect other steps in the pathogenesis of superficial siderosis.

Cochlear implantation in a patient with superficial siderosis of the central nervous system

OBJECTIVE

To perform an assessment of the viability of cochlear implantation in a patient with superficial siderosis of the brain.

STUDY DESIGN

Case review.

SETTING

Tertiary referral center.

PATIENTS

Patient with superficial siderosis of the brain.

INTERVENTION

Cochlear implantation.

MAIN OUTCOME MEASURES

Electrically evoked auditory brainstem responses and fitting strategy for cochlear implant based on patient's subjective responses.

RESULTS

After some time, C levels and T levels showed a pattern comparable with the evoked auditory brainstem responses.

CONCLUSIONS

Bilateral profound hearing loss after superficial siderosis of the brain is no absolute contraindication for implantation. Furthermore, evoked auditory brainstem measurements can potentially guide the fitting process of the implant in difficult cases.

Patterns of immunocytochemical staining for ferritin and transferrin in the human spinal cord following traumatic injury

Normally Fe(2+) is strictly controlled within the central nervous system (CNS) because of its potential to react with oxygen and form free radicals.(1,2) Traumatic spinal cord injury (TSCI) leads to cell damage and haemorrhage, both of which may increase the pool of free iron.(3) The aim of this study was to examine the response to TSCI of the iron storage protein ferritin (Ft) and the iron transport protein transferrin (Tf). The study found a significant increase in Ft positive cells compared to controls and a significant correlation between the number of Ft positive cells and the severity of injury. Significantly fewer Tf positive cells were seen in the trauma cases compared to the control and there was no relation with the severity of injury. These observations suggest a disturbance in normal iron metabolism within the spinal cord following injury, with possible implications for free radical mediated secondary damage.

Marginal siderosis and degenerative myelopathy: a manifestation of chronic subarachnoid hemorrhage in a horse with a myxopapillary ependymoma

Marginal siderosis is recognized in humans as an uncommon clinicopathologic entity characterized by degeneration of neural tissue at the surface of the brain and spinal cord, in association with the accumulation of hemosiderin, and resulting from chronic subarachnoid hemorrhage. The sources of hemorrhage are various and include neoplasms, malformations, cysts, and vasculopathy. Marginal siderosis of the spinal cord due to a myxopapillary ependymoma was diagnosed in a 19-year-old Dutch Warm Blood horse with clinical signs of myelopathy. There is only one previous report of marginal siderosis in the veterinary literature, also in a horse with clinical myelopathy.

Surgical management of superficial siderosis following cervical nerve root avulsion

Neurosensory hearing loss, ataxia, spastic paraparesis, sphincter dysfunction, somatosensory disturbances, and cognitive effects are associated with superficial siderosis of the central nervous system caused by chronic intrathecal bleeding. We describe superficial siderosis that developed more than a decade following traumatic brachial nerve root avulsion. While cerebrospinal fluid analysis indicated chronic intrathecal bleeding, angiography did not localize a specific source. Surgical intervention that included repair of a meningeal diverticulum and venous cauterization resulted in overall reduction, but not complete elimination, of central nervous system bleeding.

Superficial siderosis of the central nervous system

Two patients with superficial siderosis of the central nervous system are reported. Both developed progressive deafness over many years; one with associated anosmia and partial seizures; the other with progressive ataxia and diplopia. The cerebrospinal fluid was xanthochromic in one and the protein was raised in both. Magnetic resonance imaging revealed a hypodense rim around the eighth cranial nerve, cerebellum, brain stem and spinal cord. Despite extensive investigations the cause of the superficial siderosis in both patients remains undetermined.

beta-alanine uptake is upregulated in FeCl3-induced cortical scars

Glial uptake of beta-[14C]alanine (beta-Ala) was studied in male Sprague-Dawley rats after sub-pial iontophoresis of FeCl3 into the right motor strip. Models bearing a 15-day-old scar were selected because of the presence of strongly reactive glia induced by FeCl3. Behavioral seizures were observed by daily visual inspection in one third of the animals. The effects of intraperitoneal (i.p.) injections of DL-alpha-aminoadipic acid (DLaAA), which exerts specific gliotoxicity through glutamine synthetase (GS) inhibition, and of 3-mercaptoproprionic acid (3MP), a potent inhibitor of glutamic acid decarboxylase (GAD: the rate-limiting enzyme in the biosynthesis of gamma-aminobutyric acid [GABA]), were also examined. There was significant enhancement of beta-Ala uptake in the margins of the scars. Further increases of uptake were triggered by 3MP, and there was extensive recruitment of astrocytes within isocortex even at a distance from the edges of the scar. DL-alpha-Aminoadipic acid caused a slight decrease of beta-Ala uptake, which was selectively localized to the scar margins. Seizure activity was unchanged by high i.p. doses of DL alpha AA. Our results strongly suggest that beta-Ala has high affinity for normal and reactive astrocytes, and that the uptake can be significantly enhanced by lowering endogenous GABA levels in abnormal cortical tissues in and around FeCl3-lesions by inhibition of GAD. Enhancement of glial beta-Ala uptake appeared to depend heavily on increased endothelial transport of small neutral amino acids, in a process modulated by perivascular glia. This model of free radical neurotoxicity may help gain more insight into abnormal neuronal-glial interactions caused by lipid peroxidation.

The cellular reactions to experimental intracerebral hemorrhage

The resolution of an intracerebral hemorrhage can be measured by the occurrence of hemosiderin. Extravasation of blood elicits a cellular reaction in the adjacent surviving tissue where the lesion activates resident microglia and attracts many more phagocytes from the blood stream. The signals for this migration into the perifocal reactive zone are not fully understood but it is likely that proteins in the coagulated blood contribute to cellular activation. In order to study the role of plasma proteins in the pathogenesis of the perifocal reactive zone, intracerebral injections of either autologous whole blood (0.1 ml) or an equal volume of washed autologous red blood cells (RBC) in lactated Ringer's solution were made in adult rabbits. The amount of total iron was the same (30 micrograms). The cellular responses to the injections were studied by iron histochemistry and immunocytochemistry for ferritin, the ferritin repressor protein (FRP), the glial fibrillary acidic protein (GFAP), and the complement receptor CR3. Experimental hematomas resolved much more slowly after the injection of whole blood than after the injection of RBC. Qualitative microglial and astrocytic responses were quite similar. However, at 48 h, iron- and ferritin-reactive microglia were more numerous following the injection of whole blood. After injections of either type, ferritin-immunoreactive cells were more abundant than iron-positive cells. This observation implied that the biosynthesis of holoferritin protein and iron incorporation proceeded independently. Expression of CR3 on the surface of microglia was much more prominent after whole blood, suggesting a role of inactivated complement 3b in the attraction of additional phagocytes. Conversion to hemosiderin began at 5 days after the injection of either blood or RBC. The lesions caused initial destruction of astrocytes in the perifocal zone as judged by GFAP- and FRP-immunoreactivity. However, at 5 days, astrocytic processes reentered the perifocal zone and intermingled with microglia and macrophages. It is proposed that this contact between astrocytes and microglia reversed the uncoupling of ferritin biosynthesis and iron incorporation and initiated the storage of iron and formation of hemosiderin.

Cellular management of iron in the brain

All organs including the brain contain iron, and the proteins involved in iron uptake (transferrin and transferrin receptor) and intracellular storage (ferritin). However, because the brain resides behind a barrier and has a heterogeneous population of cells, there are aspects of its iron management that are unique. Iron management, the timely delivery of appropriate amounts of iron, is crucial to normal brain development and function. Mismanagement of cellular iron can result not only in decreased metabolic activity but increased vulnerability to oxidative damage. There is regional specificity in cell deposition of iron and the iron regulatory proteins. However, the sequestration of iron in the brain seems primarily the responsibility of oligodendrocytes, as these cells contain most of the stainable iron in the brain. Transferrin, the iron-mobilizing protein, is also found predominantly in these cells. The transferrin receptor is abundantly expressed on blood vessels, large neurons in the cortex, striatum, and hippocampus, and is also present on oligodendrocytes and astrocytes. Ferritin, the intracellular iron storage protein, consists of 2 subunits which are functionally distinct, and we provide evidence in this report that the cellular distribution of the ferritin subunits is also distinct. In addition, changes in the cellular distribution of iron and its associated regulatory proteins occur in Alzheimer's disease. Neuritic plaques contain relatively large amounts of stainable iron, and the surrounding cells robustly immunostain for ferritin and the transferrin receptor. Analysis of the cellular distribution of iron indicates the different levels of requirement of iron in the brain by different cell types and should ultimately elucidate how cells acquire and maintain this essential component of oxidative metabolism. In addition, changes in the ability of cells to deliver and manage iron may provide insight into altered metabolic activity with age and disease as well as identify cell populations at risk for iron-induced oxidative stress.

The microglial cell. A historical review

Effectively, modern research has confirmed Hortega's view of the origin of the microgliacyte from circulating monocytes of the monocyte-macrophage series that invade the brain during embryonic and early postnatal life. Their phagocytic capacity is exercised during the brain remodelling that marks brain maturation. They then convert to the ramified resting microglial cell visualized in the silver carbonate staining technique of Hortega and by modern lectin-binding methods. In response to injury, reactive microglia exhibit hypertrophy and hyperplasia, and may or may not go on to form typical lipid-laden phagocytes. Activated microglia show upregulation of the many marker antigens they share with circulating monocytes, including the major histocompatibility class (MHC) class II antigens that bespeak their immunocompetent nature. However, MHC class I and II expression and development of immunohistochemical positivity for cytoplasmic and plasma membrane antigens that characterize the monocyte-macrophage do not necessarily indicate an immunological response though there is ample evidence that microglia can serve as antigen-presenting cells. Rather, microglia are extraordinarily sensitive to changes in the brain microenvironment, whatever the nature of the exciting mechanism or substance. They may be considered to serve an ever alert, protective and supportive function that can be assembled rapidly to deal with infections, physical injuries, physiologic changes and systemic influences. In addition to elaboration and secretion of cytokines with varied actions, e.g., suppression of astrogliosis, they secrete factors, including nerve growth factor, which are supportive of neurons. They have an important role in iron metabolism and the storage of iron and ferritin. They may promote central nervous system regeneration. They are prominently involved in such pathologic processes as the acquired immunodeficiency syndrome, multiple sclerosis, prion diseases and the degenerative disorders, e.g., Alzheimer's disease and Parkinson's disease. With aging, they grow more numerous, become richer in iron and ferritin and exhibit phenotypic alteration, e.g., the expression of MHC class II antigens that are not ordinarily demonstrable immunohistochemically in the resting state. The rate of growth of our knowledge of microglia during the last decade has been exponential and continues.

Superficial siderosis of the central nervous system: a case with an unruptured intracranial aneurysm

We present a case of superficial siderosis (SS) of the central nervous system (CNS) with an unruptured intracranial aneurysm to illustrate that the commonly encountered unexplainable progressive sensorineural hearing loss (SNHL) can be an important sign for the early awareness of this rare disorder. The literature on SS is reviewed and the pathogenesis of SS is discussed.

The pathogenesis of superficial siderosis of the central nervous system

In advanced cases of superficial siderosis of the human central nervous system, the clinical triad of hearing loss, cerebellar ataxia, and myelopathy permits the diagnosis at the bedside, and magnetic resonance imaging readily confirms the hemosiderin deposits in brainstem, cerebellum, and spinal cord. To study the pathogenesis of this condition and explain the selective vulnerability of the cerebellum, experimental siderosis was induced in rabbits by the repeated intracisternal injection of autologous red blood cells. The earliest cellular response in the cerebellar molecular layer was hyperplasia and hypertrophy of microglia as displayed by immunocytochemistry for ferritin. Microglia also contained iron, but ferritin biosynthesis appeared to proceed without commensurate iron accumulation. This early apoferritin response probably occurred due to the presence of heme, rather than iron, in the cerebrospinal fluid and subpial tissue. Ferritin biosynthesis is accelerated when the ferritin repressor protein is dissociated from ferritin messenger ribonucleic acid. A specific antiserum localized ferritin repressor protein predominantly to astrocytes including Bergmann glia. It is proposed that abundance and proximity of ferritin repressor protein--immunoreactive Bergmann glia and ferritin-containing microglia in the cerebellar molecular layer permit prompt cellular interaction in the conversion of heme to ferritin and ultimately hemosiderin.