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BMJ Case Rep. 2010; 2010: bcr06.2009.1975.
Published online 2010 March 23. doi:  10.1136/bcr.06.2009.1975
PMCID: PMC3027775
Reminder of important clinical lesson

Chronic optic disc swelling overlooked in a diabetic patient with a devastating outcome

Abstract

We present a case of asymmetrical but bilateral, progressive, painless visual deterioration over 5 years to no perception of light, in a 61-year-old male diabetic patient referred for a second opinion. The patient had a chronic history of bilateral diabetic maculopathy and unexplained swelling of the optic discs. He was diagnosed with optic atrophy secondary to pseudotumour cerebri (termed idiopathic intracranial hypertension when underlying causes have been excluded), which was associated with obstructive sleep apnoea. The case highlights the critical importance of identifying and investigating chronic papilloedema for reversible causes; the sometimes subtle presentation of pseudotumour cerebri; and the vital role of visual field testing and diagnostic lumbar puncture for timely diagnosis. It also reminds us that chronic bilateral optic disc swelling is not a normal feature of diabetic eye disease, and that alarm bells should sound if reduced visual acuity seems disproportionate to the degree of maculopathy.

Background

The case history and images obtained from 5 years preceding referral highlight important lessons about the presentation and investigation of chronic optic disc swelling, and the devastating outcome that may result without treatment.

Case presentation

A 61-year-old Caucasian man presented for a specialist opinion with a 5 year history of painless, gradually progressive, asymmetric vision loss. His background included well controlled type 2 diabetes mellitus of 14 years duration and hypertension of 19 years duration.

Outpatient records and imaging collected over 9 years in three hospitals were reviewed to gain a detailed history. Bilateral background diabetic retinopathy had first been detected 9 years earlier. Five years earlier visual acuity (VA) fell to 6/9 bilaterally, with evidence of bilateral macular oedema, which was treated with bilateral focal argon laser therapy following fundus fluorescein angiography (fig 1). This resulted in improvement of the right eye’s VA to 6/6, but had no impact on the left eye, which gradually deteriorated over 12 months to counting fingers vision. Later that year the patient presented with a 5 day history of reduced right VA (6/24), and bilateral fullness of the optic discs was noted, with dilation of superficial disc capillaries. Elevated intracranial pressure was not suspected, but he was empirically commenced on the carbonic anhydrase inhibitor acetazolamide, 250 mg daily, perhaps to improve perfusion of the swollen discs through reduction of aqueous production and lowering of intraocular pressure. During the following month the right VA normalised, and the dose was reduced to 125 mg.

Figure 1
Labelled fundus fluorescein angiography performed 5 years before presentation: images 1 and 2 are colour photographs of the right and left fundi, respectively; image 3 is taken in the ‘early venous phase’ in the left fundus; images 4 and ...

At follow-up the next year, the right VA was 6/7.5 and the left VA had improved slightly to 3/60. He received multiple focal argon laser treatments to both eyes, the left in particular, for active diabetic maculopathy. Pronounced disc swelling persisted bilaterally, so the acetazolamide was increased again to 250 mg, and a computed tomography (CT) scan of the head and orbits without contrast was performed to exclude intracranial pathology. This was reported as normal, along with subsequent magnetic resonance imaging (MRI) of the head and a Doppler ultrasound study of the carotid arteries. Lumbar puncture was not performed.

At routine follow-up the next year (3 years before referral to our hospital), the right VA had deteriorated to 6/12, despite no increase in maculopathy, and increased swelling and pallor of the right disc was noted. The cause of this deterioration was uncertain, but non-arteritic ischaemic optic neuropathy or diabetic papillopathy were suspected, and the acetazolamide dose was further increased to 250 mg twice daily. Over the next 12 months the right VA fluctuated around 6/12 and 6/18. At the patient’s request, repeat trials of tapered systemic prednisolone were tried, followed by repeat intraorbital triamcinolone (40 mg), and then a 3 month trial of hyperbaric oxygen therapy, though the rationale for these is unclear: systemic steroids frequently worsen glycaemic control and can precipitate intracranial hypertension on withdrawal, among other side effects. The right eye vision continued to deteriorate to 6/60.

Four months before admission, bilateral disc pallor and swelling were noted, with a left relative afferent pupillary defect, and visual acuities of 1/60 on the right, and ‘hand movements’ on the left. Around this time, the patient discontinued acetazolamide, after 4 years, as he felt it was not helping. Two months before admission his vision had further deteriorated, to no perception of light in the left eye, and light perception only in the right. On admission he had no perception of light in either eye. No previous visual field records were available for review.

The patient volunteered no associated symptoms, but on direct questioning admitted to neck ache on waking most mornings for several months, which he attributed to his pillow and poor sleeping position. He admitted a long history of snoring, and more recent daytime somnolence. He had been overweight for many years, and had recently gained further weight. There were no other symptoms.

In addition to well controlled type 2 diabetes and hypertension, his previous medical history included tooth extraction 30 years earlier, complicated by an oro-maxillary sinus communication and recurrent sinusitis until a repair operation and nasal septoplasty 7 years later. He was otherwise fit and well. His regular medications included sertraline, aspirin, doxazosin, valsartan, rosiglitazone, glimepiride, metformin, alpha lipoic acid and ginkobiloba. He had no allergies, and there was no family history of note. He had worked with computers until 18 months previously, when declining vision in his better eye forced him to retire. He lived alone, managing with help from neighbours. He was an ex-smoker with a 15 pack-year history, and consumed approximately 14 units of alcohol per week.

General examination revealed a body mass index (BMI) of 31 kg/m2, but was otherwise unremarkable. Ophthalmic examination showed a mild convergent squint, and reduced VA to no perception of light bilaterally. The pupil reactions were absent to light and present to accommodation. Digital colour photographs of the fundi are shown in infigsfigs 2 and 3. The intraocular pressures were normal.

Figure 2
Labelled digital colour photograph of the right fundus.
Figure 3
Labelled digital colour photograph of the left fundus.

Differential diagnosis

1. Clinically significant diabetic macular oedema

This may account for significant loss of visual acuity,1 in the left eye especially in this case. However, it is not associated with chronic optic disc swelling, which was apparent in the fundus fluorescein angiogram (FFA) images taken 5 years earlier. It is also not associated with total loss of light perception.

2. Ischaemic central retinal vein occlusion (CRVO)

Early optic disc swelling typically occurs in this condition, accompanied by extensive retinal haemorrhages and cotton wool spots, with subsequent disc neovascularisation and retinochoroidal collateral vessels.2 These were not present in this case, and the patient’s history of gradual deterioration in vision bilaterally, with fluctuation, rather than acute deterioration, was also against CRVO.

3. Non-arteritic anterior ischaemic optic neuropathy

This may present with painless subacute or chronic stepwise, sequential vision loss, which may not recover, in patients >50 years with diabetes and hypertension.3 Segmental swelling of the optic disc is frequently seen, with prominent dilated capillaries over the disc, and peripapillary haemorrhages.

4. Diabetic papillopathy

This is usually an asymptomatic condition affecting younger patients with diabetes, although it has also been reported in older patients with type 2 diabetes.4 It is associated with significant capillary non-perfusion and macular oedema.4 Examination reveals a swollen, hyperaemic optic disc and peripapillary capillary dilatation.4 Bilateral vision loss is rare, and recovers spontaneously over months, leaving mild optic atrophy.4

5. Intracranial hypertension

While this condition most frequently presents in younger women, with a classic triad of headache, tinnitus, and visual obscurations, it may present in older males and with a more subtle history. Visual disturbance occurs due to papilloedema, which may progress to field restriction and eventual optic atrophy and blindness.5 With chronicity, the elevated pressure in the subarachnoid space interrupts axoplasmic transport in the optic nerve which may lead to the appearance of axonal degradation products, ‘corpora amylacea’, on the swollen optic nerve head (fig 4) and retinochoroidal collateral vessels.5 The history of chronic, fluctuating but progressive vision loss in an obese individual with intermittent morning neck ache, and visual improvement on acetazolamide, were suggestive of this diagnosis.

Figure 4
Labelled digital colour photograph of the left optic disc revealing a corpora amylacea at 2 o’clock.

Investigations

  • The HbA1c was 6.0% (4–6%), and all other laboratory investigations were unremarkable.
  • CT of the orbits and head with contrast was performed and initially reported normal (fig 5). Re-reporting noted distended optic nerve sheaths and posterior scleral flattening.
    Figure 5
    Labelled computed tomography image of the orbits with features consistent with idiopathic intracranial hypertension visible on the left in this slice.
  • Lumbar puncture performed after the patient had been off acetazolamide for 2 months revealed an elevated opening pressure of 36.5 cm H20 with normal cerebrospinal fluid analysis.
  • Overnight polysomnography was performed, and confirmed a degree of obstructive sleep apnoea (OSA); during the 7 h study, 58 dips >4% were recorded, with a mean nadir of 91%, and lowest saturation of 82%. In a second overnight sleep study, lasting 10 h, the patient tolerated continuous positive airway pressure (CPAP) non-invasive ventilation. He had a reduction in the number of dips, with just 10 of >4%, and a mean nadir of 92%.

Treatment

A diagnosis of pseudotumour cerebri was made, with possible connection to obesity and sleep disturbance, and the patient was recommenced on 250 mg acetazolamide four times daily, and sent home for a trial of CPAP.6

Outcome and follow-up

The patient returned 5 weeks later reporting no recovery of vision, although his morning neck pain had stopped. Lumbar puncture revealed that the cerebrospinal fluid (CSF) pressure was still elevated, at 39.5 cm H20, and so a lumbo-peritoneal shunt was inserted. No vision was recovered in the subsequent months.

Discussion

Idiopathic intracranial hypertension

Idiopathic intracranial hypertension (IIH) is a poorly understood syndrome in which symptoms and signs of raised intracranial pressure, in the absence of causative lesions on neurological imaging, can present floridly, or develop very gradually.5 The alternative name for this syndrome, pseudotumour cerebri, is arguably more appropriate when it occurs in association with cerebral venous thrombosis, chronic renal failure, systemic lupus erythematosis, obstructive sleep apnoea in men, or various documented prescription drugs including tetracycline.5,6 The term ‘benign’ is no longer used, as 10–20% of patients develop visual impairment from papilloedema over weeks or months.5 IIH has an incidence of 1 per 100 000 per year, but this increases to 19 per 100 000 per year in the group at greatest risk, namely women aged 20–44 years who are 20% or more over their ideal body weight.5

The modified Dandy criteria for the diagnosis of IIH include: the presence of raised intracranial pressure >20 cm H20, measured in the lateral decubitus position; the absence of an identifiable cause; normal CSF composition; no evidence of hydrocephalus, mass, structural, or vascular lesions; and the presence of symptoms and signs indicative of generalised intracranial hypertension or papilloedema only.5 There are no pathognomonic radiological signs, and while numerous markers have been identified, including pre-laminar enhancement and vertical tortuosity of the orbital optic nerves, distension of the perioptic subarachnoid space, intra-sellar herniation of the arachnoid (“empty sella”) and posterior scleral flattening, only the latter has a high specificity and positive predictive value.7 CT or magnetic resonance venography are important to exclude cerebral venous sinus thrombosis when the presentation is more acute.5

The common geographic and administrative separation between ophthalmology and neurology services can hinder timely diagnostic lumbar puncture. In addition, the procedure may be technically challenging on account of the frequently high BMIs in this patient population, and radiological guidance may be required. Quantitative serial perimetry is essential to monitor clinical progression, and may reveal inferonasal defects, arcuate scotoma and progressive field restriction.5 Helpful additional investigations include fluorescein angiography, which shows leakage of dye from the optic disc, serial disc photography, and ocular CT of the swollen peripapillary retinal nerve fibre layer.5

The chief goal of treatment is to prevent vision loss by reducing intracranial pressure, and current medical therapy includes diuretics, carbonic anhydrase inhibitors (eg, acetazolamide), serial lumbar puncture, and managed weight loss. In more severe cases surgical intervention may be necessary, with optic nerve sheath fenestration or insertion of lumbo- or ventriculo-peritoneal shunts.8 In cases where the syndrome is associated with obstructive sleep apnoea, nocturnal CPAP may be effective.6

Pseudotumour cerebri and obstructive sleep apnoea

Several retrospective case series have identified that OSA and other sleep related breathing problems are common in men meeting the diagnostic criteria for IIH, and various physiological mechanisms have been proposed.6 The prevalence of OSA in men is unknown, but estimates range from 0.4–5.9%.6 It is characterised by recurrent partial or complete upper airway obstruction during sleep leading to excessive daytime somnolence, loud snoring and periodic apnoea with interruption of airflow, nocturnal hypoxia, hypercarbia, hypertension, and arterial oxygen desaturation.6 Apnoeic episodes may occur hundreds of times per night, lasting seconds to minutes, and are terminated by arousal from sleep. The diagnosis is confirmed by overnight polysomnography, and treatments include weight loss, nocturnal oxygen therapy, nocturnal nasal CPAP, and upper airway/oropharyngeal surgery.6 These interventions may improve the signs and symptoms of pseudotumour cerebri if the conditions are diagnosed early.6

Summary

In this case, progressive visual failure with disc swelling over 5 years, resulting from unrecognised pseudotumour cerebri, was misattributed to bilateral diabetes associated non-arteritic ischaemic optic neuropathy. At presentation the patient had complete bilateral optic atrophy with no perception of light, and treatment to normalise the intracranial pressure, and treat the OSA, came too late to improve vision. Pseudotumour cerebri is a relatively common, treatable cause of blindness, and this case highlights the importance of close collaboration between ophthalmologists and neurologists, and timely intervention.

Learning points

  • Chronic papilloedema from any cause can lead to significant visual impairment and blindness if left untreated.
  • Chronic disc swelling with subsequent pallor are not a feature of diabetic eye disease.
  • Pseudotumour cerebri may present a diagnostic challenge because the onset and course can be insipid, with non-specific symptoms, and subtle clinical and radiological signs.
  • Lumbar puncture, to measure the opening CSF pressure, is the most important diagnostic test, but can be misleading if the raised intracranial pressure is intermittent.
  • Serial perimetry (visual field testing) is essential to monitor clinical progression.

Footnotes

Competing interests: None.

Patient consent: Patient/guardian consent was obtained for publication.

REFERENCES

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2. Hayreh SS. Prevalent misconceptions about acute retinal vascular occlusive disorders. Prog Retin Eye Res 2005; 24: 493–519. [PubMed]
3. Fontal MR, Kerrison JB, Garcia R, et al. Ischemic optic neuropathy. Semin Neurol 2007; 27: 221–32. [PubMed]
4. Regillo CD, Brown GC, Savino PJ, et al. Diabetic papillopathy. Patient characteristics and fundus findings. Arch Ophthalmol 1995; 113: 889–95. [PubMed]
5. Acheson JF. Idiopathic intracranial hypertension and visual function. Br Med Bull 2006; 79–80: 233–44. [PubMed]
6. Lee AG, Golnik K, Kardon R, et al. Sleep apnea and intracranial hypertension in men. Ophthalmology 2002; 109: 482–5. [PubMed]
7. Agid R, Farb RI, Willinsky RA, et al. Idiopathic intracranial hypertension: the validity of cross-sectional neuroimaging signs. Neuroradiology 2006; 48: 521–7. [PubMed]
8. Ball AK, Clarke CE. Idiopathic intracranial hypertension. Lancet Neurol 2006; 5: 433–42. [PubMed]

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