AIMS AND OBJECTIVES:
The presented study had to objectives:
- To study the change in optic nerve diameter in patients with acute rise in intracranial pressure and to compare it with control population.
- To correlate optic nerve sheath diameter with outcome of disease in patients with hepatic encephalopathy.
INTRODUCTION:
THE INTRACRANIAL PRESSURE
Raised intracranial pressure (ICP) plays major role in increasing mortality in various clinical conditions,
such as trauma,
hemorrhage,
hydrocephalus,
and hepatic failure and therefore,
forms a major consideration in management of these patients.
However,
techniques presently used to monitor ICP are expensive,
invasive and associated with many complications.
We therefore,
decided to look for feasibility of non-invasive technique to monitor ICP.
Table 1:Non invasive techniques being investigated for ICP monitoring:
S.N.
|
Technique
|
Available literature
|
1.
|
Venous opthalmodynamometry
|
(a) Firsching R.
et al.32
(b) Motschman et al. 33
|
2.
|
Transcranial Doppler Ultrasonography
|
(a) Nadvi SS.
et al.34
|
3.
|
Computerized tomography
|
(a) Schoeman J.F.
et al.30
|
4.
|
High-resolution magnetic resonance imaging of the intraorbital optic nerve
|
(a) Mashima Y.
et al.38
|
5.
|
Tympanic membrane displacement audiometric technique
|
(a) Marchbanks RJ et al.39
(b) Samuel M,
Burge DM,
Marchbanks RJ40
(c) Moss SM,
Marchbanks RJ,
Burge41
|
6.
|
Assessment of IOP as a measure of raised ICP
|
(a) Ralph A.W.
et al.42
|
7.
|
Relationship between scalp blood flow and intracranial pressure.
|
(a) H.
Eskandary,
H Reihani,
H Najafipour43
|
8.
|
Visual evoked potentials : A non-invasive technique to monitor patients with raised ICP
|
(a) Sklar FH et al.44
|
9.
|
Pulsed phase-lock loop (PPLL) technology.
|
(a) The NASA NDE Working Group21
|
10.
|
Ultrasonography of the optic nerve sheath
|
(a) Blaivas M.
et al.70
(b) Gangemi M et al.67
(c) Brezezinska R.
et al.68
(d) Newman W.D.
et al.69
|
It is obvious that any method that is used for ICP monitoring must carry minimal or no risk of complication and at the same time such a method should be simple,
cost effective,
sensitive and reproducible.
Among the techniques which may be used for ICP monitoring,
ultrasound seems to fulfill all these prerequisite.
Therefore,
in the present study we investigated the effectiveness of sonography in detection of optic nerve expansion in hepatic failure patient and whether sonologically detected optic nerve sheath expansion can act as a prognostic marker in hepatic failure patients
Many authors have studied role of B-mode sonography in evaluation of orbital tissue.
Most of these studies have concentrated on space occupying lesions of eyeball and retro orbital tissue.
However,
in our department comment on optic nerve diameter is routinely made in all B-mode examinations of orbit.
We have frequently observed that optic nerve diameter is commonly increased in certain subgroups of patients of hepatocellular disease.
Most of these patients suffer from Grade 3 or Grade 4 hepatic encephalopathy (HE). One wonders,
what makes optic nerve to dilate in these patients (of hepatic encephalopathy)?
It has been firmly established that cerebral edema and resultant intracranial hypertension (ICHT) is most important factor that contributes to increased mortality,
failure of orthotropic liver transplant and poor prognosis in hepatic failure patients.
Thus it is obvious to presume that optic nerve dilatation,
frequently observed in HE patients with poor prognosis is likely to be due to ICHT.
Dilatation of optic nerve sheath in hydrocephalus and head trauma patients with CT evidence of raised ICT and hepatic failure patients scheduled for orthotropic liver transplant has been reported in literature.
Hansen & Helmke,
convincingly demonstrated dilatation of optic nerve in patients with experimentally induced ICHT.
They also demonstrated effectiveness of sonography in sensitively detecting this optic nerve sheath expansion.