1,721,069 research outputs found
Neuroprotective role of neurophysiological monitoring during endovascular procedures in the brain and spinal cord
No full textThe goal of endovascular neurosurgery is to occlude aneurysms and arteriovenous malformations (AVMs) or to reduce the vascular supply to hypervascularized tumors, while preserving function in the normal neural tissue. However, the intra-arterial injection of embolizing materials into the cerebral or spinal circulation exposes to the risk of ischemic complications. Under general anesthesia, unless a wake-up test is performed, the only way to assess the functional integrity of sensory and motor pathways is to use neurophysiological monitoring. Somatosensory (SEPs) and muscle motor evoked potentials (mMEPs) can be used in combination with pharmacological provocative tests (PTs) to predict the effects of embolization. Amytal((R)) blocks neuronal activity, while lidocaine blocks axonal conduction. Therefore, a positive Amytal((R)) or lidocaine test (i.e. more than 50\% decrease in SEP amplitude and/or mMEP disappearance) indicates that the vessel distal to the tip of the microcatheter supplies the functional gray or white matter of the spinal-cord respectively and cannot be embolized. Brain and spinal-cord vascularization and hemodynamics are extremely complex and even more unpredictable in the presence of a vascular malformation, but using a combined SEPs, MEPs and PTs protocol, morbidity related to endovascular procedures is very low. Given the high sensitivity of peripheral recordings to spinal-cord ischemia, experimental and clinical studies support the concept that whenever the mechanism of spinal-cord injury is purely ischemic, recording mMEPs may suffice. Reports on the use of PTs and neurophysiological monitoring during embolization of brain AVMs in critical areas are more anecdotal and mainly limited to the use of short-acting barbiturates. Our preliminary experience using lidocaine and combining SEP and mMEP monitoring is encouraging, since no false negative results were observed. Finally, if the sensitivity of this method is very high, its specificity has not been tested because embolization is abandoned whenever PTs are consistently positive. Accordingly, the possibility of false positive results cannot be excluded
Intracranial myxoid chondrosarcoma with early intradural growth
No full textChondrosarcomas are extremely rare intracranial cartilaginous tumors of which the myxoid variant is the least reported in the literature. They develop extradurally and generally infiltrate the dura only in advanced stages or at recurrence. We describe the case of a 55-year-old woman with a posterior cranial fossa myxoid chondrosarcoma which had a primarily intradural extension
Demystifying the role of magnetic resonance in identifying intraocular foreign bodies: a case of ocular siderosis
Full text linkBackground: Ocular siderosis (OS) is a significant cause of visual loss due to retained ferrous intraocular foreign bodies (IOFB). Despite its rarity, OS can lead to severe visual impairment if not promptly diagnosed and treated. This case is notable due to the occult nature of the IOFB, which was undetected by standard imaging modalities, emphasizing the critical role of magnetic resonance imaging (MRI) in such scenarios.
Case presentation: A 51-year-old Caucasian male presented with progressive vision loss in his right eye over 20 days. Best corrected visual acuity (BCVA) was 20/1000 in the right eye and 20/20 in the left eye. Intraocular pressure (IOP) was 9 mmHg in both eyes. Slit-lamp examination revealed a small linear corneal wound and an iris defect in the right eye, along with a cataract featuring brownish deposits on the anterior capsule. The left eye was normal. Fundus examination of the right eye was hindered by media opacities. Ultrasonography showed a flat retina and choroid with no detectable IOFB. Despite a strong clinical suspicion of OS, computed tomography (CT) did not detect any IOFB. MRI subsequently identified an artifact in the inferior sectors of the right eye, indicative of a metallic IOFB. Surgical intervention involved a 23-gauge vitrectomy, phacoemulsification, IOFB removal and silicon oil (SO) tamponade resulting in a fully restored VA of 20/20 and normal IOP one month post-operation. SO was removed 2 months later. The retina remained adherent with no PVR development, and optical coherence tomography (OCT) scans showed a normal macula.
Conclusions: This case underscores the importance of considering OS in patients with unexplained vision loss and history of ocular trauma, even when initial imaging fails to detect an IOFB. MRI proved crucial in identifying the IOFB, highlighting its value in the diagnostic process. Early detection and surgical removal of IOFBs are essential to prevent irreversible visual damage. This case demonstrates that MRI should be employed when CT and ultrasonography are inconclusive, ensuring accurate diagnosis and timely intervention to preserve vision
Paradoxically greater interhemispheric transfer deficits in partial than complete callosal agenesis
No full textSymptoms of interhemispheric disconnection are typically much less severe in callosal agenesis than after surgical section of the corpus callosum. Sperry [Sperry, R. W., Plasticity of neural maturation. Developmental Biology, 1968, 2 (Suppl.), 306-327.] has attributed this difference to two interconnected factors: (1) the callosal section is usually performed after the brain has lost the maximal degree of functional plasticity associated with the early stages of development and (2) the removal of an already formed structure is more disruptive for functional brain organization than the failure of the same structure to develop. It has been suggested that functional compensation is less efficient if callosal agenesis is partial rather than complete [Dennis, M., Impaired sensory and motor differentiation with corpus callosum agenesis: A lack of callosal inhibition during ontogeny? Neuropsychologia, 1976, 14, 455-469.]. This suggestion is supported by the present findings of partial left-hand anomia, partial left-field alexia and poor tactile cross-localization in a subject with a congenital absence of the posterior part of the corpus callosum due to an arteriovenous malformation. In agreement with many previous studies, similar, though more severe, symptoms of interhemispheric disconnection were found in a subject with a complete section of the corpus callosum, but not in a subject with complete callosal agenesis. Praxic control of the left hand on verbal commands was severely deficient in the callosotomy subject, but it was normal in the subject with callosal hypogenesis. The lesser degree of compensation in partial compared to complete callosal agenesis may be explained by a reduced pressure to develop extracallosal means of interhemispheric communication, contingent on the partial existence of callosal connections, as well as by the later occurrence in development of the causes of callosal hypogenesis compared to those of total callosal agenesis
Temporary and permanent signs of interhemispheric disconnection after traumatic brain injury
No full textThe corpus callosum is frequently damaged by closed head traumas, and the resulting deficits of interhemispheric communication may vary according to the specific position of the lesion within the corpus callosum. This paper describes a single case who suffered a severe traumatic brain injury resulting in a lesion of the posterior body of the corpus callosum. Among the classical symptoms of interhemispheric disconnection, left hand anomia, left upper limb ideomotor dyspraxia, left visual field dyslexia and dysnomia, and left ear suppression in a dichotic listening task were observed shortly after the injury but recovered completely or almost completely with the passage of time. The only symptom of interhemispheric disconnection which was found to persist more than 4 years after the injury was an abnormal prolongation of the crossed-uncrossed difference in a simple visuomotor reaction time task. This prolongation was comparable with that observed in subjects with complete callosal lesions or agenesis. The results suggest that the posterior body of the corpus callosum may be an obligatory interhemispheric communication channel for mediating fast visuo-motor responses. The transient nature of other symptoms of interhemispheric disconnection suggests a relatively wide dispersion of fibers with different functions through the callosal body, such that parts of them can survive a restricted lesion and allow functional recovery of hemispheric interactions. An assessment of the evolution in time of symptoms of interhemispheric disconnection following restricted callosal lesions may reveal fine and coarse features of the anatomo-functional topography of the corpus callosum
Neurolinguistic and follow-up study of an unusual pattern of recovery from bilingual subcortical aphasia
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