Optic Neuritis (ON)

Epidemiology

- onset: teens to 40s

- female > male

- incidence 1-6/100,000

- 40% of multiple sclerosis (MS) patients have had ON, 10-15% as the first presentation of MS

- 50% of patients with ON will have an abnormal MRI at presentation

Etiology

idiopathic, demyelinating / MS, infectious (e.g. viral), post-viral or vaccination

DDx

- Ischemic: anterior ischemic optic neuritis, central retinal artery occlusion, temporal arteritis

- Compressive / Infltrative (orbital, optic nerve or pituitary): neoplastic, dysthyroid

- Hereditary: Leber's, Freidreich's

- Toxic / Nutritional: B12/B1 deficiency, methanol, lead, benzene

- Inflammatory / Infectious: SLE, sarcoid, syphilis, lyme, Bartonella (Cat-Scratch disease)

History

- acute or subacute onset

- visual loss, usually monocular

- progresses over 1-2 weeks then gradually recovers over weeks to months

- periocular pain or pain with eye movements (70-90%)

- pain settles before visual loss recovers

- impaired color perception

- colors appear dull, pale, washed-out or darker

- phosphenes (perceptions of flashes of light) sometimes occur with eye movement

- also inquire about previous transient neurological symptoms, l’Hermitte’s or Uhthoff’s symptoms (worsening of neurological symptoms with increase in body temperature)

Examination

- decreased visual acuity

- relative afferent pupillary defect (RAPD; Marcus Gunn pupil) on swinging light test

- can quantitate the RAPD by placing neutral density filters of increasing density over the unaffected eye until the pupillary responses are equal

- funduscopic examination

- usually normal (retrobulbar neuritis)

- papillitis (<10%)

- optic disc pallor, indicating optic atrophy, may develop with resolution of symptoms

- visual scotoma

- usually central but arcuate and altitudinal defects may be seen

- altered / impaired color vision

- use Ishihara color plates

- alternatively test grossly at bedside comparing the color of a red object between each eye

- misperception of trajectory of objects on swinging pendulum test (Pulfrich phenomenon)

- image of a pendulum swinging left to right appears to move away and toward affected subject

- Hot bath test (historical) may unmask or worsen visual acuity / afferent defect in optic neuritis (secondary to reversible conduction block in demyelinated fibers)

- look for associated abnormalities on neurological examination (e.g. internuclear ophthalmoplegia, pyramidal weakness, sensory loss, ataxia, etc.)

Prognosis

Visual Acuity:

- worsens over 3-7 days, improves over weeks to months

- 50% full recovery at 1 month, 75% at 6 months

- prognosis worsens with severity of visual loss and is worse in painless ON

ON recurrence:

- 15% at 2 years, can be either eye

Development of MS:

- overall risk varies from 17-85% in longitudinal studies with incomplete follow-up

- In Optic Neuritis Treatment Trial, rates were:

	5 year	10 year
Overall	30%	38%
No lesions on MRI	16%	22%
Lesions on MRI	37% (1-2 typical lesions) 51% (3 or more typical lesions)	56% (1 or more typical lesions)

- factors that increase the risk of developing MS after ON:

- the presence of lesions on MRI head

- prior transient neurological symptoms, e.g. paresthesias (these patients probably have MS already!)

- HLA DR3 and DR2

- CSF oligoclonal banding

Investigations

1. MRI brain / orbits +/- gadolinium:

- optic nerves will appear hyper-intense on T2 and will enhance with gadolinium

- also useful to screen for other lesions in the brain parenchyma which may represent MS plaques (see MS topic for description of appearance and location)

2. Consider lumbar puncture:

- clear, colorless, normal pressure

- WBC normal in 2/3, >15 cells/ml in <5%, >50 cells/ml very rarely; predominantly lymphocytes

- protein and glucose usually normal

- consider sending CSF for oligoclonal banding, IgG index and IgG / albumin ratio (see MS topic for further discussion)

3. Consider VEP (visual evoked potentials):

- abnormal in 90% of patients with ON (even when visual acuity has returned to normal)

Management

- controversial

- consider either:

1) no treatment, monitoring

2) prednisone 1 mg/kg/d PO OD x 11 days followed by a 4 day taper

3) IV methylprednisolone 1g/d x 3 days then prednisone 1 mg/kg/d PO OD x 11 days followed by a 4 day taper

NOTES:

· Treatment with steroids ONLY speeds recovery of visual function. It has no effect on ON recurrence and only a transient effect on development of MS (¯ 2 year risk but not 5 year risk)

· Treat based on patient preference, occupation, severity of symptoms and risks of treatment e.g. GI hemorrhage, infection, hypertension, fluid retention, hypokalemia, psychosis, worsen DM control, avascular necrosis of hip

· Newer trials suggest that treatment of ON patients with interferon may be beneficial in those patients at high risk of developing MS. Fewer patients convert to MS at 2 years follow-up. Unclear whether interferon therapy reduces the overall risk of progression to MS. (ETOMS study Lancet 357:1576, 2001 and CHAMPS Am.J.Ophthalmol.132:463, 2001)

Bilateral simultaneous ON

- rare

- more often associated with a post-infectious or post-vaccination etiology

Devic’s disease or neuromyelitis optica

- Optic neuropathy and myelopathy occurring simultaneously or closely together in time

- Controversial whether this is a variant of MS or a separate clinical entity

- Rare syndrome in Western countries, more frequently seen in Orient

- May be seen as a first presentation of MS, as well as in ADEM (acute disseminated encephalomyelitis), SLE, Sjogren’s syndrome and other viral and bacterial infections (EBV, VZV, HIV, tuberculosis)

References:

Am. J. Ophthalmol. 2001 132:463

Neurol. 2000 54:2039

J. Neurol. 2000 247:435

MS. Paty and Ebers. Vol. 50 Contemporary Neurology Series, 1998

Last update: January 2004

Reviewed by: Dr. G. Rice

Neurological Medicine Pocketbook

© 2003-2004 UWO Neurology Residents

http://www.uwo.ca/cns/resident

All Rights Reserved

Disclaimer