Method and apparatus for measuring intracranial fluid pressure
First Claim
1. A method of serially monitoring the intracranial fluid pressure of a subject which comprises alternately obtaining measurements related to the magnitude and direction of the volume displacement of an ear drum in response to induced stapedial muscle contraction and the acoustic compliance of said eardrum when pressure on opposite sides thereof is equalised by tympanometry, and using said measurements serially to monitor the intracranial fluid pressure of the subject.
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Abstract
Intracranial fluid pressure is measured as a function of a characteristic or characteristics of an eardrum. Either or both of the displacement of the eardrum when the stapedius muscle is stimulated or the aural acoustic compliance of the eardrum is measured and provided the cochlear aqueduct is open this will give an indication of intracranial fluid pressure without surgery. Acoustic compliance is measured under conditions of tympanometry but the tympanometry facility is disabled during displacement measurement. The data obtained by the method of the invention may be compared with reference data obtained from the same patient or in clinical trials to provide a real-time record of intracranial fluid pressure changes. Preferably eardrum displacement is used as a baseline measure and acoustic compliance measurement records short-term variation, the two records being combined by computer. Reference data may be input to the computer to update the information displayed. This reference data may include known variations determined by surgery or caused by a postural manoeuvre of the patient.
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Citations
16 Claims
- 1. A method of serially monitoring the intracranial fluid pressure of a subject which comprises alternately obtaining measurements related to the magnitude and direction of the volume displacement of an ear drum in response to induced stapedial muscle contraction and the acoustic compliance of said eardrum when pressure on opposite sides thereof is equalised by tympanometry, and using said measurements serially to monitor the intracranial fluid pressure of the subject.
- 6. Apparatus for serially monitoring intracranial pressure comprising means for the acoustic stimulation of a stapedial muscle, means for obtaining a measurement related to the magnitude and direction of the responsive volume displacement of the associated ear drum, means for comparing said measurement with pre-established reference data derived from the measurement of intracranial fluid pressure by other means and read-out means to display the results of said comparison.
- 9. Apparatus for serially monitoring intracranial fluid pressure comprising tympanometry means, means for obtaining a measurement related to the acoustic compliance of an ear drum while under the influence of said tympanometry means, means for disabling the tympanometry means, means for stimulating contraction of the stapedial muscle associated with said ear drum and for obtaining a measurement related to the magnitude and direction of the responsive volume displacement of said ear drum, means for actuating said measurement means alternately with said tympanometry means and means for obtaining a measurement related to the acoustic compliance disabled when obtaining a measurement related to said ear drum displacement, and means for using said measurement related to the magnitude and direction of the responsive volume displacement of said ear drum to monitor intracranial fluid pressure.
- 12. A method of serially monitoring the intracranial fluid pressure of a subject, which comprises providing measuring means for obtaining a measurement related to the magnitude and direction of volume displacement of an ear drum, generating and applying to an ear drum an acoustic signal sufficient to stimulate contraction of the stapedial muscle, operating said measuring means to obtain a measurement related to the magnitude and direction of volume displacement of the ear drum in response to said stapedial muscle contraction, and using said measurement to monitor the intracranial fluid pressure of the subject.
Specification