Value of visual evoked potential monitoring during trans-sphenoidal pituitary surgery

Chacko, Ari G; Babu, K. Srinivasa; Chandy, Mathew J.

doi:10.1080/02688699650040133

Cited by 59 publications

(31 citation statements)

References 12 publications

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“…Patients with pituitary tumors offer a new model for understanding both the process of spontaneous remyelination in the human brain and the functional consequences of that remyelination, and therefore, provide new leverage on the development of biomarkers for secondary white matter injury. This is significant, because as noted above, there have been notable failures to predict the likelihood of visual recovery following decompression of retinofugal nerves: factors such as tumor size, duration of compression, severity of pre-surgical visual impairments, and age do not predict visual outcome (10-12). Previous neuro-ophthalmologic research on macroadenoma patients (15, 37) using pattern electroretinography (PERG), photopic negative response (PhNR) and retinal nerve fiber layer (RNFL) thickness has found that PERG is able to predict only failure of visual recovery (38), whereas post-operative PhNR and RNFL thickness significantly correlate with visual field outcomes at three to six months (15).…”

Section: Discussionmentioning

confidence: 99%

White matter changes linked to visual recovery after nerve decompression

et al. 2014

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The relationship between the integrity of white matter tracts and cortical function in the human brain remains poorly understood. Here we use a model of reversible white matter injury, compression of the optic chiasm by tumors of the pituitary gland, to study the structural and functional changes that attend spontaneous recovery of cortical function and visual abilities after surgical tumor removal and subsequent decompression of the nerves. We show that compression of the optic chiasm leads to demyelination of the optic tracts, which reverses as quickly as 4 weeks after nerve decompression. Furthermore, variability across patients in the severity of demyelination in the optic tracts predicts visual ability and functional activity in early cortical visual areas, and pre-operative measurements of myelination in the optic tracts predicts the magnitude of visual recovery after surgery. These data indicate that rapid regeneration of myelin in the human brain is a significant component of the normalization of cortical activity, and ultimately the recovery of sensory and cognitive function, after nerve decompression. More generally, our findings demonstrate the utility of diffusion tensor imaging as an in vivo measure of myelination in the human brain.

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Section: Discussionmentioning

confidence: 99%

White matter changes linked to visual recovery after nerve decompression

et al. 2014

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“…While some authors only see very limited use of VEP-monitoring under surgery at all [4][5][6][7][8], others have published optimistic results [9][10][11][12][13]. There is agreement on the need of further improvement regarding stimulation characteristics, recording technique, and anesthesiological management.…”

Section: Introductionmentioning

confidence: 94%

Fourier transformed steady-state flash evoked potentials for continuous monitoring of visual pathway function

et al. 2007

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Monitoring of somatosensory, motor and auditory pathway function by evoked potentials is routine in surgery placing these pathways at risk. However, visual pathway function remains yet inaccessible to a reliable monitoring. For this study, a method of continuous recordings was developed and tested. Steady-state visual evoked potentials were elicited by flash stimulation at 16 Hz and analysed using discrete Fourier transform. Amplitude and phase of the fundamental response were dynamically averaged and continuously plotted in a trend graph. The method was applied on awake individuals with normal vision and on patients undergoing neurosurgery. In most individuals it was possible to continuously record significant responses. Surprisingly, characteristic time-courses of amplitude and phase were observed in several subjects. These findings were attributed mainly to flicker-adaptation. During anesthesia, amplitude and signal-to-noise ratio were markedly smaller. Signal recognition was facilitated when potentials were recorded with a subdural electrode placed directly at the occipital pole. The anesthetic agent propofol had a major impact on the recordings.

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“…There were four studies that reported statistical data only regarding severity of vision loss. Two reported no significant association 50,69 and two reported significant association. One of these showed r ¼ 0.656 (p < 0.001), 13 and the other described a "significant correlation" 49 with no further description of the analysis.…”

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confidence: 91%