British Journal of Radiology (2004) 77, 897-898
© 2004 British Institute of Radiology
doi: 10.1259/bjr/29657815
A pathognomonic MRI finding in a patient with ataxia and hearing loss
O Kilickesmez, MD
Radiology Department, Dort D Millet Hospital, Ugur Mumcu cad. No:6, 59860 Corlu, Tekirdag, Turkey
Correspondence: Ozgur Kilickesmez, Bahcelievler 4. Aralik 5/5 A.Dereli Apt. Corlu, Tekirdag, 59860-TR, Turkey
A 14-year-old female patient presented with symptoms of ataxia, bilateral hearing loss and weakness of both upper and lower extremities, which had been evident for the last year. She had been operated on twice in the last 6 years for cerebellar medulloblastoma. MRI of the brain was performed. What distinctive imaging features are present (Figure 1
)? What is the diagnosis?
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Figure 1. (a) Axial spin echo T1 weighted image. (b) Axial post-contrast spin echo T1 weighted image. (c) Axial spin echo proton density weighted image. (d) Coronal spin echo T2 weighted image.
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MRI detected typical post-operative changes due to a previous suboccipital craniectomy (not shown here), of marked and diffusely thickened dura. Additionally, on the proton density and T2 weighted (T2W) sequences of the brain, a dark signal intensity rim outlining the hemispheres, pons and cerebellar peduncles and bordering the subarachnoid cisterns, representing hemosiderin, was seen (Figure 1
). The radiological diagnosis was superficial siderosis of the central nervous system meninges. Cerebrospinal fluid (CSF) analysis of the patient revealed increased ferritin and iron levels.
Superficial siderosis is a rare condition consisting of deposition of hemosiderin on the leptomeninges, as well as on the surface of the brain, cerebellum, brain stem and cranial nerves. The most common reported clinical symptoms are: hearing impairment (95%), cerebellar ataxia (88%), pyramidal signs (76%), dementia (24%), anosmia (17%), anisocoria (10%) and sensory signs (13%). Less frequent symptoms include backache and lower motor signs (5–10%). Two types of superficial siderosis are described in the literature: idiopathic and secondary superficial siderosis [1]. The common sources of subarachnoid bleeding causing secondary superficial siderosis are: dural abnormalities, vascular lesions and tumours, as well as post-traumatic or post-surgical lesions. Neonatal superficial siderosis has been described with striking MRI findings secondary to single massive intraventricular haemorrhage [2]. Among the current theories proposed to explain superficial siderosis in idiopathic cases is increased permeability of meningeal arteries with passage of red blood cells into the CSF. A second potential cause is bleeding from angiographically occult vascular malformations. The areas of the brain that are most severely affected include the superior vermis, brain stem and cortex, especially around the Sylvian cisterns. Pathologically there is deposition of hemosiderin in those parts of the central nervous system that are in close proximity to CSF. Iron in the form of ferritin is highly toxic and may cause neural death and reactive gliosis. Astrocytes and microglia are responsible for uptake of excessive CSF iron in superficial siderosis. Over time, the iron pigments infiltrate the underlying neural tissue and may in turn result in necrosis of the crest of the cerebellar folia and the vermis. It is thought that the cochlear nerve and the cerebellar cortex are particularly vulnerable owing to their accelerated ferritin synthesis. Routine laboratory studies of patients are typically unremarkable. CSF examination reveals haemorrhage and xanthochromia in approximately half of cases. The diagnosis should be considered in patients who present with slowly developing hearing loss and ataxia many years after surgery. Increased numbers of red blood cells, an increased level of siderophages, xanthochromia and high concentrations of proteins in the CSF support the diagnosis, however MRI appears the technique of choice to confirm the diagnosis. The hypointense rim typically seen on T2W images and coating the cerebellum, brain stem, cranial nerves, cerebral hemispheres and/or spinal cord is produced by the strong magnetic susceptibility effect of iron. This effect is more pronounced at T2*W sequences [3, 4]. This appearance is pathognomonic. The optimum treatment is ablation of the bleeding source, however no source is detected in most cases. Chelation of iron with desferroxiamine or trientene may reduce CSF iron levels, but clinical improvement often remains unsatisfactory. In conclusion, MRI is the most sensitive and specific technique in detecting and confirming the disease [1, 5].
Received for publication May 10, 2004.
Accepted for publication August 13, 2004.
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References
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- Kumar A, Aggarwal S, Willinsky R, TerBrugge KG. Posterior fossa surgery: an unusual cause of superficial siderosis. Neurosurgery 1993;32:455–7.[Medline]
- Glasier CM, Garcia-Thomas GI, Allison JW. Superficial CNS siderosis in the newborn: MR diagnosis. Pediatr Radiol 1999;29:76–7.[Medline]
- Marin H, Vargas MI, Bogorin A, Lenz V, Warter JM, Jacques C, et al. Siderosis of the brain and spinal cord. Report of two cases. J Neuroradiol 2003;30:60–4. [In French.][Medline]
- Uchino A, Aibe H, Itoh H, Aiko Y, Tanaka M. Superficial siderosis of the central nervous system. Its MRI manifestations. Clin Imaging 1997;21:241–5.[CrossRef][Medline]
- Aferzon M, Greene JS. Radiology forum: quiz case 1. Diagnosis: superficial siderosis. Arch Otolaryngol Head Neck Surg 2001;127:714–6.[Free Full Text]
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