|
DISCUSSION
Optic perineuritis (OPN) is also known as perioptic neuritis, and describes inflammation of optic nerve sheath without inflammation of the optic nerve itself [4,5]. The inflammation is assumed to affect the optic nerve sheath only when there is evidence of optic nerve dysfunction with normal intracranial pressure [5]. Recently, the optic perineuritis has been focused on the idiopathic inflammatory response of optic nerve sheath [4,5]. Optic perineuritis occasionally occurs as a manifestation of specific infectious or inflammatory disorder, eg. Wegener granulomatosis, giant cell arteritis or initial presentation of sarcoidosis [6,7].
Optic perineuritis is a rare presentation and it is one subclassification of idiopathic orbital inflammation or orbital pseudotumor [1]. Other orbital structures that may be involved are lacrimal gland (dacryoadenitis), extraocular muscles (myositis), sclera (scleritis) or orbital fat [1]. Idiopathic orbital inflammation involving the orbital apex is called TolosoHunt syndrome [1]. It typically produced painful external ophthalmoplegia regardless of cavernous sinus involvement [1]. Acute onset of orbital pain, limited ocular motility and proptosis are characteristic presentations of idiopathic orbital inflammation after excluding other secondary inflammations or infections [1]. Some patients do not present classical signs and symptoms of orbital pseudotumor, making orbital imaging a vitally important investigation to ascertain the diagnosis [1]. As in our case, patient presented with minimal inflammation of conjunctiva with markedly reduced optic nerve function and ocular motility. However, there was no sign of proptosis. So, clinically it was difficult to distinguish between optic perineuritis and retrobulbar optic neuritis.Most of clinical features of patient with OPN are also likely to be misdiagnosed of having optic neuritis (ON) [4]. However, demographic data of optic perineuritis show most patients with OPN are women with broader range of age (36% are more than 50 years old) [4]. The mean age of OPN patients is older than patients with optic neuritis [4]. Pattern of visual loss is also different in a patient with OPN compared to ON. In OPN patient visual loss progresses over several weeks before the correct diagnosis is made and commonly has sparing of central vision [4], while in ON patient the visual loss progresses within few days and sparing of central vision is less common.
In OPN, the inflammation of extraocular muscle causes motility disturbance as occurred in this patient. Other signs that may help to diagnose OPN are subtle ptosis, chemosis and diplopia (orbital involvement) [4]. In contrast to ON patient, abnormal eye motility and the other signs mentioned are not typical features unless it is associated with brainstem involvement due to multifocal demyelinating disease [5]. However, some patients with OPN also do not have any proptosis or ophthalmoplegia which mimic retrobulbar optic neuritis [8,9].
The diagnosis of OPN is typically based on combination of clinical and radiographic imaging findings particularly magnetic resonance imaging (MRI) [4]. Optic nerve biopsy is not indicated in most cases of suspected OPN [1,4]. The characteristic pattern in neuroimaging of OPN typically shows enhancement of optic nerve sheath (“tramtrack” on axial view and "doughnut" on coronal view) as found in our patient [4]. There was presence of streaky enhancement of orbital fat [9] and it was also found in her MRI. In another published case report of OPN, MRI showed enhancement of optic nerve substance due to inflammation of intraneural pial septa and optic nerve sheath [9]. These changes in neuroimaging are not found in patients with typical demyelinating ON. Those radioimaging findings are best obtained from MRI scans specifically the use of dedicated orbital views with fat suppression and gadolinium [9]. Computed tomographic scanning, however, does not usually give adequate spatial resolution to distinguish perineural enhancement from intraneural enhancement as found in demyelinating ON [4]. Furthermore, the highresolution CT imaging is associated with radiation exposure and may put risk to other mortality or morbidity due to iodinated contrast [9].
It is important to differentiate between OPN and ON for two reasons. The treatment and prognosis are different. Patient with OPN will respond to corticosteroids or anti inflammatory agents and may need to prolong the treatment to prevent recurrence. If not treated, the patient will continue to lose vision. In contrast with ON, the treatment is more controversial[10].
Corticosteroids have not been proven to influence the visual outcome and many patients did not receive the treatment in OPN. The route of administration and dosage are also different. In OPN, oral corticosteroid with the dosage of 80mg/day is recommended but contraindicated in ON because it may increase the rate of recurrence of optic neuritis [11]. The course of corticosteroid treatment in ON is shorter (two weeks) but it is not long enough for OPN.
The prognosis of OPN is generally excellent [4]. The patients having OPN are not at risk of developing multiple sclerosis but are likely to have recurrent visual loss in future. Compared to ON patients, they are at high risk of developing multiple sclerosis and need to counsel.
In conclusion, optic perineuritis is a rare presentation of idiopathic orbital inflammation syndrome that clinically may mimic retrobulbar optic neuritis. Early diagnosis to differentiate the two clinical entities will result in better management and improve the visual prognosis.
【参考文献】
1 American Academy of Ophthalmology. Basic and clinical science course: orbit, eyelids, and lacrimal system. Section 7. San Francisco: AAO; 20022003
2 Noble SC, Chandler WF, Lloyd RV. Intracranial extension of orbital pseudotumor: a case report. Neurosurgery1986;18:798801
3 Kaye AH, Hahn JF, Cracium A, Hanson M, Berlin AJ, Tubbs RR. Intracranial extension of inflammatory pseudotumor of the orbit. Case report. J Neurosurg1984;60: 625629
4 Purvin V, Kawasaki A, Jacobson DM. Optic perineuritis: clinical and radiographic features. Arch Ophthalmol2001;119:12991306
5 Miller NR, Newman NJ. The essentials. Walsh & Hoyts Clinical NeuroOphthalmology. 5th ed. Lippincott Williams & Wilkins; 1999
6 Nassani S, Cocito L, Arcuri T, Favale E. Orbital pseudotumor as a presenting sign of temporal arteritis. Clin Exp Rheumatol1995;13:367369
7 YuWaiMan P, Crompton DE, Graham JY, Black FM, Dayan MR. Optic perineuritis as a rare initial presentation of sarcoidosis. Clin Exp 上一页 [1] [2] |
