Case report – Pseudopapilloedema Caused by Optic Disc Drusen in a 10 year old boy
Abstract
An otherwise health 10 year old boy presented with apparent optic disc oedema. Fundus examination using a slit lamp and OCT were used to rule out papilloedema and diagnose pseudopapilloedema due to optic disc drusen.
Introduction
Due to the similarity in presentation with papilloedema optic disc drusen (ODD) in children can cause unnecessary diagnostic procedures and anxiety (Chang & Pineles, 2016). This case study discusses the diagnosis of a 10 year old boy referred to the clinic for suspected papilloedema who was found to have pseudopapilloedema due to ODD. New imaging technology has added to the options available to clinicians for the detection and diagnosis of ODD in children (Hamann, Malmqvist, & Costello, 2018). The importance of detection of ODD and the various methods that can be used to do so are discussed.
Case Study
A 10 year old Caucasian male (Patient W) presented to the clinic following a routine visit to the optometrist who noted pale optic discs. A paediatrician, on fundus examination, had subsequently diagnosed oedematous optic discs and sent Patient W for a Magnetic Resonance Imaging (MRI) scan. Patient W had been non-compliant with the MRI.
On presentation to the clinic Patient W had no visual complaints, headaches or nausea. He was in good health and it was noted that he was prescribed 20mg a day of methylphenidate hcl (Ritalin) to assist with concentration at school, past ocular history was unremarkable and it was noted that his Grandfather has glaucoma. Patient W had an uneventful birth history. He reported no difficulty with the board or reading at school. His vision using a Snellen chart was 6/6 each eye, colour vision using the Ishihara chart and pupils were normal. Patient W’s mother was very anxious following failure to obtain a MRI and rule out a sinister cause for the apparent oedematous discs.
On examination of the fundus the ophthalmologist found full discs with no obvious swelling and requested an Optical Coherence Tomography (OCT) scan of the discs.
Imaging was captured using the Zeiss Cirrus HD -OCT 500 utilising the High Definition 5-Line Raster scan of the optic disc. As Patient W suffers difficulty concentrating the more detailed 21 line scan could not be obtained at this visit. The images showed no subtle signs of subretinal fluid which could indicate true papilloedema. The optic nerve head was found to have features consistent with ODD in both eyes. Combined with the clinical picture which did not indicate any signs of raised intracranial pressure the diagnosis of psuedopapilloedema due to ODD was explained to the family. It was suggested that MRI scans under sedation were not required at this stage and further OCT scans of the optic disc would be conducted in 6 months time to ensure that the clinical picture was not evolving.
Discussion
ODD are found in up to 2.4% of the general population (Malmqvist, Li, et al., 2017). The pathophysiology is relatively unknown (Malmqvist, Li, et al., 2017) it is known that they are hyaline deposits within the optic nerve which over time become calcified (Bowling, 2016). They are generally located anterior to the laminar cribrosa and behind Bruch’s membrane (Leon, Hutchinson, Lenhart, & Lambert, 2014). 2/3 of ODD are bilateral and ODD are more common in females and Caucasians (Chang & Pineles, 2016). ODD can be transmitted as an autosomal dominant trait (Brodsky, 2016).
In children the prevalence is thought to be 0.4% – 1.0% (Chang & Pineles, 2016). ODD in children are generally asymptomatic (Chang & Pineles, 2016) and buried therefore ODD in children are more difficult to detect (Malmqvist, Bursztyn, et al., 2017) and it is likely that childhood occurrence could be underestimated (Malmqvist, Li, et al., 2017). It is suggested that ODD begin deep in the optic nerve and move superficially over time (Malmqvist, Lund-Andersen, & Hamann, 2017). As a person ages ODD are thought to increase in size and calcification levels (Bowling, 2016) thus making them most likely to be diagnosed by around the age of 12 (Chang & Pineles, 2016).
ODD are commonly associated with and thought to be an early presenting sign of retinitis pigmentosa, pseudoxanthoma elasticum, angioid streaks, Usher syndrome, Noonan syndrome and Algille syndrome (Bowling, 2016; Brodsky, 2016; Tuğcu & Özdemir, 2016). Therefore on finding ODD in children these issues should be ruled out (Brodsky, 2016).
Complications associated with ODD are thought to be rare (Bowling, 2016) and include visual field loss particularly in the inferonasal quadrant, blind spot enlargement, concentric constriction, arcuate defects or peripheral vision loss (Tuğcu & Özdemir, 2016). Slowly developing visual field loss may be associated with retinal nerve fibre thinning which is typically found nasally in association with ODD (Chang & Pineles, 2016). The most common cause of acute vision loss associated with ODD is due to nonarteritic anterior ischaemic optic neuropathy (NAION) found without systematic risk factors and often in the late teens or early 20’s (Chang & Pineles, 2016; Tan & Tow, 2013). Later in life complications can include vitreous, retinal and disc haemorrhage often found with associated choroidal neovascularisation (Bowling, 2016; Tuğcu & Özdemir, 2016).
ODD are often initially misdiagnosed as papilloedema due to the presentation of optic disc oedema (Chang & Pineles, 2016). Optic disc oedema can be broadly categorized as papilloedema or pseudopapilloedema. Papilloedema is swelling of the optic disc secondary to intracranial pressure (Brodsky, 2016). When papilloedema is suspected it is necessary to investigate fully in order to rule out a sinister cause such as tumour casing the raised intracranial pressure (Chang & Pineles, 2016). Generally papilloedema is suspected when a child presents with bilateral optic disc elevation without visual loss but with headaches, nausea and vomiting (Brodsky, 2016).
Pseudopapilloedema is described when blurring of the nasal disc margins are found in a child with no other health complaint and it is suspected to be caused by actual or apparent elevation of the optic discs due to local structural factors (Brodsky, 2016). When a child presents with apparent swollen discs it is important to rule out ODD in order to prevent extensive and unnecessary testing such as MRI scans and lumbar puncture procedures (Şahin, Cingü, Ari, Çinar, & Çaça, 2012). In the USA in 2014 it was found that mean diagnostic work up costs for ODD were 3 times more expensive when neuroimaging or lumbar puncture were performed before optic disc imaging (Leon et al., 2014). In Patient W’s case trying to obtain an MRI had caused him distress and failure to obtain an MRI image had caused his mother significant anxiety. It was suggested that Patient W’s next step would be to repeat the MRI under sedation or anaesthesia which was causing both Patient W and his mother further anxiety. In this case that the costs associated with the MRI scan could have been avoided if the OCT scan had been performed first. However finding ODD does not necessarily rule out elevated intracranial pressure as an underlying or pre-existing condition therefore other signs and symptoms must also be considered before ruling out further testing (Brodsky, 2016).
Diagnosis of ODD requires a detailed examination of the optic disc at both the surface level and below in order to evaluate both superficial and deep ODD. Diagnosis can be undertaken using ophthalmascope, autoflourescence photography (FAF), Fundus fluorescein angiography (FFA), Computed tomography (CT), B-scan ultrasonography (B-scan) or OCT (Malmqvist, Li, et al., 2017). Visual defects can also be found but they are usually linked to superficial drusen and therefore tend to manifest later in life (Chang & Pineles, 2016).
The appearance of ODD under ophthalmascope varies depending on location within the optic nerve head and changes over time (Leon et al., 2014; Şahin et al., 2012). Buried ODD typically seen in children are particular difficult to identify on fundus examination (Şahin et al., 2012). Patient W experienced a concerning diagnosis following fundus examination by an optometrist and paediatrician because the ODD were buried and presented as raised or swollen optic discs, in his case further diagnosis was essential to rule out papilloedema.
FAF which is non-invasive can only be used to detect superior structures therefore its usefulness extends mostly to diagnosis in Adults. FFA can be used to differentiate oedema from deeper structures and is useful in ruling out papilloedema (Brodsky, 2016). The main disadvantage of FFA in children is its invasive nature (Tuğcu & Özdemir, 2016). Young patients may not be able to tolerate intravenous fluorescein or cooperate with image capture required for the procedure to be diagnostically useful (Chang & Pineles, 2016).
Using a CT scan the ODD will show as bright white bodies due to the calcium content (Tuğcu & Özdemir, 2016), because of this CT scans have been found to have a low sensitivity for detecting ODD in children where the drusen are not yet calcified (Bowling, 2016). This combined with concerns about radiation exposure in children means CT scans are not a preferred method for ODD diagnosis in children (Chang & Pineles, 2016).
ODD have a high reflectivity therefore a B-scan is inexpensive and fast method of diagnosis. A B-scan can detect deep structures but the resolution is low (Tuğcu & Özdemir, 2016). In children the application of cold wet gel and the need to move the eye under closed lids may cause difficulties with compliance. Previously B-scan ultrasonography was considered the gold standard imaging modality to detect ODD. However in children because the ODD are likely to be non-calcified and buried the scan is less likely to detect them (Chang & Pineles, 2016). In the case of Patient W obtaining and B-scan would likely have been complicated by his young age and lack of concentration.
Advances in OCT technology such as the Enhanced Depth Imaging OCT (EDI-OCT) have allowed deeper structures of the eye to be visualised. EDI-OCT has been found to have a higher detection rate for ODD than B-scan ultrasonography (Merchant et al., 2013) particularly in the detection of deeper ODD (Malmqvist, Bursztyn, et al., 2017). In 2017 The Optic Disc Drusen Studies Consortium published recommendations on using OCT for the diagnosis of ODD to provide reliable and consistent diagnosis for medical and research purposes (Malmqvist, Bursztyn, et al., 2017). Due to the accuracy levels achieved following the protocol combined with the non-invasive nature of EDI-OCT it is now considered the gold standard for detecting both buried and superficial ODD in adults and children (Hamann et al., 2018). The OCT scan used to diagnose the patients ODD was complicated by his difficultly concentrating but using a relatively new machine combined with an experienced operator allowed clear and detailed images to be obtained at a resolution which enabled diagnosis of his ODD.
Visual fields can be used to monitor the progression of ODD, field loss is thought to occur in 51% of children with an average detection age of 14 and becoming more common with increasing age (Chang & Pineles, 2016). However studies have found no correlation when comparing superficial ODD and degree of visual field loss (Malmqvist, Lund-Andersen, et al., 2017) so visual filed loss is not predicative of ODD nor can it be used to confirm their presence. Sight threatening visual field defects are rare (Bowling, 2016). Visual filed examination was not considered on Patient W but perhaps at future visits as he gets older this could be used to monitor any potential deterioration in his vision.
It is noted that in the literature there is limited knowledge on the mechanisms and prognosis for patients with ODD. Early diagnosis via OCT could lead to more complete studies of ODD and their progression over time. This information may also be used to develop prognosis and treatment protocols.
Conclusion
ODD should be considered as a differential diagnosis when presented with apparent optic disc oedema. ODD can be confirmed by an OCT scan of the optic disc area. If a patient presents with no other signs of papilloedema further testing is not required and the patient can be monitored for development of visual loss associated with superficial ODD. Ruling out ODD before conducting MRI or Lumbar puncture procedures can reduce health care costs and anxiety levels for patients.
References
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