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|Year : 2015 | Volume
| Issue : 2 | Page : 292-294
Role of ocular ultrasound in idiopathic intra-cranial hypertension
Jyoti Matalia, Sheetal Shirke, Minal Kekatpure
Department of Pediatric Ophthalmology and Neuro-Ophthalmology, Narayana Nethralaya-2, Bengaluru, Karnataka, India
|Date of Web Publication||5-May-2015|
Department of Pediatric Ophthalmology and Neuro-Ophthalmology, Narayana Nethralaya-2, Bengaluru, Karnataka
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Matalia J, Shirke S, Kekatpure M. Role of ocular ultrasound in idiopathic intra-cranial hypertension. Neurol India 2015;63:292-4
We came across the original article titled "Idiopathic intracranial hypertension in paediatric population: A case series from India" by Arun Roy and colleagues  while researching the literature for our pediatric patients with idiopathic intra-cranial hypertension (IIH). At the outset, we would like to congratulate the authors for this large series which is probably the first from India. The reason for writing this letter is to highlight the role of an ocular B-scan ultrasound from the neuro-ophthalmogy point of view in evaluating IIH in children. As we all know, IIH is characterized by increased intra-cranial pressure (ICP) with essentially normal brain magnetic resonance imaging (MRI) and magnetic resonance venography (MRV).  However, the presence of IIH in children offers some unique challenges. Small children may not complain of headache or diplopia. At times, it can be difficult to monitor the optic nerve function in children, especially in infants, as a formal visual acuity measurement and a visual field assessment cannot be carried out in them. The diagnosis of IIH mainly relies on the MRI study and cerebrospinal fluid opening pressure measurements, which is difficult to assess in the pediatric population. Also, these procedures need to be performed under anesthesia or sedation. MRI has a definitive diagnostic role as IIH is essentially a diagnosis of exclusion. Monitoring symptomatic improvement or ensuring resolution of papilledema by ophthalmoscopy can judge the response to therapy. Although papilledema is characteristically seen, its absence is increasingly reported in children, as was the case in the study being discussed.
Ocular B scan ultrasound is a simple yet effective tool in detecting an increased size of the optic nerve head and in the assessment of subarachnoid fluid around the optic nerve. It shows an intra-ocular elevation, specifically at the region of the optic nerve head, along with increased optic nerve sheath diameter [Figure 1]. The subarachnoid fluid can also be seen as a homogenous, echolucent crescent or as a ring-shaped area around the optic nerve [Figure 1]. The optic nerve is a part of the central nervous system with its sheath being in continuation with the dura mater. This sheath contains a potential space that communicates with the subarachnoid space. Any pressure changes in the intracranial cavity are transmitted to the optic nerve along this space, increasing the optic nerve sheath diameter.  Eventually, papilledema develops due to impedance of the axonal transport in the optic nerve as a result of the increased pressure.  Thus, increase in the optic nerve sheath diameter even prior to the development of papilledema can be picked up by the B-scan ultrasound. A review of the available literature regarding the use of ocular ultrasound and its value in the detection of increased ICP reveals a strong correlation between the optic nerve sheath and the level of ICP, with its greater diameter being strongly associated with an increased ICP.  It has widely been used in emergency medicine in the settings of acute brain injury, ,,,, and its usage has also occasionally been in the evaluation of IIH. ,
|Figure 1: B scan ultrasound of the eye showing elevation of the optic nerve head (arrowhead) and increase in the size of the optic nerve head (5.40 mm) with presence of the echolucent arachnoidal fluid in a crescent shape around it (arrow)|
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This simple tool offers various advantages. It is an outpatient procedure that does not need general anesthesia. It provides at bedside, a real-time, quantitative measurement, making it a more objective diagnostic tool. Also, ICP changes can easily be monitored over time. It can be an useful adjuvant in the diagnosis and management of patients with IIH, especially the children. An ultrasound may provide a useful alternative in determining the presence of papilledema in a patient in whom fundoscopy cannot be adequately performed or has been found to be non-diagnostic.
Therefore, in children with suspected increased ICP in whom there may be an absence of typical symptoms along with a non-diagnostic ocular examination, ultrasound can aid in the early detection of increased ICP. Moreover, in similar circumstances, when monitoring of response to therapy can be tricky due to the difficulties encountered in performing the necessary investigations to assess the visual function, ocular ultrasound can prove to be an important tool.  In summary, ocular ultrasound is a useful, easy, rapid, objective and sensitive tool to assess ICP in real time and may have an important role in diagnosing and monitoring the therapeutic response in children with IIH.
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