Surgery – Diagnostic testing – Eye or testing by visual stimulus
Reexamination Certificate
2001-04-27
2002-07-09
Hindenburg, Max (Department: 3736)
Surgery
Diagnostic testing
Eye or testing by visual stimulus
Reexamination Certificate
active
06416481
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method and apparatus for assessing the neural integrity of a patient's central nervous system.
2. Brief Description of the Prior Art
It is well known to those of ordinary skill in the art that'stimulating an eye with flickering light induces strong neural activity resulting in oxygen consumption of the human brain [Thomas, C. G.; Menon, R. S.; (1998); “Amplitude Response and Stimulus Presentation Frequency Response of Human Primary Visual Cortex Using BOLD EPI at 4 T”;
Magnetic Resonance Medicine
, 40, 203-209] and the optic nerve head of the cat [Ahmed J.; Linsenmeier, R. A.; Dunn, R. Jr.; (1994); “The Oxygen Distribution in the Prelaminar Optic Nerve Head of the Cat”;
Experimental Eye Research
, 59, 457-465]. It is also known from the literature that selective adaptation or stimulation of one eye will induce sensitivity changes in the other, contralateral eye; this phenomenon is called “interocular transfer” [Andrews T. J.; White, L. E.; Binder, D,;Purves, D.; (1996); “Temporal Events in Cyclopean Vision”;
Proceedings of the National Academy of Sciences USA
, 93, 3689-3692]. These studies imply the role of central mechanisms, e.g. the human brain, as being responsible for the control of the sensitivity changes observed in the contralateral eye. It is also reported that cerebral infarcts will induce oxygen changes measured at the level of the contralateral eye [Staedt, U.; Hutt M.; Herrmann B.; Seufzer, U.; Leweling H.; (1989); “Effect of Hemoglobin with 10% Hydroxyethyl Starch Solution (MW 200,000/9.5) on the Flow Properties of Blood, Arterial Blood Gases and Conjunctival Oxygen Partial Pressure in Patients with Cerebral Infarct”;
Infusionstherapie
, 16, 107-112].
Epilepsy, migraines with visual auras, and temporary amnesia have all been associated with cortical depression spreading (CD) in the brain, as reported in the following articles:
[Dahlem, M. A.; Engelmann, R.; Lowel, S.; Muller, S. C.; (2000); “Does the Migraine Aura Reflect Cortical Organization?;
Eur J Neurosci
, 12, 767-770];
[Donnet A.; Bartolomei, F.; (1997); “Migraine with Visual Aura and Photosensitive Epileptic Seizures”;
Epilepsia
, 38, 1032-1034];
[Kager, H.; Wadman, W. J.; Somjen, G. G.; (2000); “Simulated Seizures and Spreading Depression in a Neuron Model Incorporating Interstitial Space and Ion Concentration”;
J Neurophysiol
., 84, 495-512];
[Kaube, H.; Herzog, J.; Kaufer, T.; Dichgans, M.; Diener, H. C.; (2000); “Aura in Some Patients with Familial Hemiplegic Migraine can be Stopped by Intranasal Ketamine”;
Neurology
, 55, 139-141];
[Pantoni, L.; Lamassa, M.; Inzitari, D.; (2000); “Transient Global Amnesia; A Review Emphasizing Pathogenic Aspects”;
Acta Neurol Scand
., 102, 275-283]; and
[Sotak, C. H.; (1999); “New NMR Measurements in Epilepsy. Diffusion-Weighted Magnetic Resonance Imaging of Spreading Depression”;
Adv Neurol
, 79, 925-929].
Cortical depression spreading can be induced by stimulation and results in a widespread decrease in oxygenation of the brain followed by a change in neural potentials.
OBJECTS OF THE INVENTION
An object of the present invention is to assess the neural integrity of the central nervous system of a patient by stimulating the patient with a visual or auditory flickering stimulus and detecting oxygenation changes in at least one eye of the patient.
SUMMARY OF THE INVENTION
More specifically, in accordance with the present invention, there is provided a method for assessing neural integrity of a patient's central nervous system, comprising stimulating the patient with a visual or auditory flickering stimulus, sensing oxygenation in at least one eye of the patient, and detecting whether a change in the sensed oxygenation occurs in response to stimulation of the patient with the flickering stimulus. This change is indicative of neural integrity of the patient's central nervous system.
Also in accordance with the present invention, there is provided an apparatus for assessing neural integrity of a patient's central nervous system, comprising a generator of a visual or auditory flickering stimulus, and a neural integrity assessment instrument responsive to oxygenation in at least one eye of the patient. The flickering stimulus is applied to the patient to stimulate this patient, and the neural integrity assessment instrument comprises:
a sensor of oxygenation in at least one eye of the patient; and
a detector of a change in the level of the sensed oxygenation in response to stimulation of said patient with the flickering stimulus, this change being indicative of neural integrity of the patient's central nervous system.
The present invention further relates to method for assessing neural integrity of a patient's central nervous system, comprising stimulating a first eye of the patient with a flickering light, sensing oxygenation in the patient's second eye, and detecting whether a change in the sensed oxygenation occurs in response to stimulation of the patient's first eye with flickering light, this change being indicative of neural integrity of the patient's central nervous system.
In accordance with preferred embodiments of this method:
sensing oxygenation in the patient's second eye comprises sensing levels of oxygenation at the optic nerve head of the fundus of the patient's second eye; and
stimulating the patient's first eye comprises adjusting at least one of the following parameters to generate at least one desired neural response of the patient's central nervous system: an intensity of the flickering light, a contrast of the flickering light, a color of the flickering light, a flicker rate of the flickering light, and a duration of the stimulation of the patient's first eye with flickering light.
The present invention still further relates to an apparatus for assessing neural integrity of a patient's central nervous system, comprising a generator of flickering light applied to a first eye of the patient to stimulate this patient's first eye, and a neural integrity assessment instrument responsive to oxygenation in the patient's second eye. The neural integrity assessment instrument comprising:
a sensor of oxygenation in the patient's second eye; and
a detector of a change in the level of the sensed oxygenation in response to stimulation of the patient's first eye with flickering light, this change being indicative of neural integrity of the patient's central nervous system.
According to preferred embodiments of this apparatus:
the sensor is positioned to sense levels of oxygenation at the optic nerve head of the fundus of the patient's second eye;
the generator comprises a source of light operated through a flickering-light controller, the source of light is selected from the group consisting of a light-emitting diode and a laser, and a fiber optic cable is interposed between the source of light and the patient's first eye to guide light from the source of light to the patient's first eye; and
the neural integrity assessment instrument comprises an on-line oxygenation measurement device.
Still further in accordance with the present invention, there is provided a method for assessing neural integrity of a patient's central nervous system, comprising stimulating at least one ear of the patient with an auditory flickering stimulus, sensing oxygenation in at least one eye of the patient, and detecting whether a change in the sensed oxygenation occurs in response to stimulation of the patient's at least one ear with the auditory flickering stimulus, this change being indicative of neural integrity of the patient's central nervous system.
According to a preferred embodiment, stimulating the patient's at least one ear comprises adjusting at least one of the following parameters to generate at least one desired neural response of the
Diaconu Vasile
Faubert Jocelyn
Fay Kaplun & Marcin LL
Hindenburg Max
Universite de Montreal
LandOfFree
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