Fundamentals of transorbital sonographic evaluation of optic nerve sheath expansion under intracranial hypertension
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The optic nerve, ontogenetically part of the central nervous system, is surrounded by subarachnoidal cerebrospinal fluid (CSF) and dura mater. Because of the connection with the intracranial subarachnoidal space, CSF pressure variations influence the optic nerve sheath (ONS) diameter. Histologic studies revealed a segment of the optic nerve in which maximal diameter fluctuations could be expected, namely the bulging dura mater region approximately 3 mm behind the papilla. Twenty preparations of optic nerves obtained post mortem were examined sonographically before and after dilatation of the ONS, by means of measurement from three different projections. After gelatine-induced widening of the subarachnoidal space, the mean diameter increased by 60 % at 3 mm behind the optic nerve head, but only by 35 % at 10 mm distance. Independent measurements by two examiners correlated highly, which indicates excellent reproducibility of the sonographic measurements. The optimal experimental scanning position was at a right angle to the optic nerve (longitudinal section). Under clinical conditions, however, only axial sections can be obtained using anterior probe positions with transbulbar sound directions. Using such axial projections the 3 nm7 position proved reliably reproducible. The reduced resolution of the optic nerve itself, allowing it to be distinguished from its surrounding sheath, proved to be somewhat disadvantageous from this projection angle.
KeywordsOptic Nerve Subarachnoidal Space Dura Mater Intracranial Hypertension Optic Nerve Head
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- 1.Marshall LF, Bowers-Marshall S, Klauber MR, et al (1991) A new classification of head injury based on computerized tomography. J Neurosurg 75: 14–20Google Scholar
- 2.Murphy A, Teasdale E, Matheson M, Galbraith S, Teasdale G (1983) Relationship between CT indices of brain swelling and intracranial pressure after head injury. In: Ishii S, Nagai H, Brock M (eds) Intracranial pressure, vol 5. Springer, Berlin Heidelberg New York, pp 562–563Google Scholar
- 5.Ghajar JBG (1986) A guide for ventricular catheter placement. Technical note. Neurosurgery 63: 54–59Google Scholar
- 13.Byrne SF (1978) The echographic measurement and differential diagnosis of optic nerve lesions. In: Ossoinig KC (ed) Ophthalmic echography. (Doc Ophthalmol Proc series, vol 48) Nijhoff/Junk, Dordrecht, pp 571–585Google Scholar
- 15.Ossoinig KC, Cennamo G, Byrne SF (1981) Echographic differential diagnosis of optic-nerve lesions. In: Thijssen JM, Verbeek AM (eds) Ultrasonography in ophthalmology. (Doc Ophthalmol Proc series, vol 29) Junk, The Hague, pp 327–332Google Scholar
- 16.Skalka HW (1981) Ultrasonography of the optic nerve. Neuroophthalmology 4: 261–272Google Scholar
- 17.Schröder W, Guthoff R (1981) Ultrasonography of the optic nerve. In: Thijssen JM, Verbeek AM (eds) Ultrasonography in ophthalmology. (Doc Ophthalmol Proc series, vol 29) Junk, The Hague, pp 359–362Google Scholar
- 18.Ossoinig KC (1993) Standardized echography of the optic nerve. In: Till P (ed) Ophthalmic echography, vol 13. Kluwer Academic, The Netherlands, pp 3–99Google Scholar
- 19.Guthoff R, Triebel G, Schröder W, Onken C, Abramo F (1990) Evaluation of the subarachnoidal space — comparisons between ultrasound and high resolution NMR-techniques. In: Sampolesi R (ed) Ultrasonography in ophthalmology, vol 12. Kluwer, Dordrecht, pp 55–62Google Scholar