any mechanism often report that their droopy lid is worse later in the day and when they are tired.

Diagnosis: Levator dehiscence

Tip: In a patient with ptosis, normal levator function implies aponeurotic ptosis, whereas subnormal levator function indicates neurogenic or myogenic ptosis.

Painful ptosis and diplopia

Case: A 48-year-old healthy secretary developed severe pain over the left brow accompanied by vertical diplopia. Examination revealed mild left upper lid ptosis, left hypotropia and limited elevation of the left eye (Figure 2.14). The remainder of her ophthalmic and neurologic examination was normal. She received a diagnosis of superior division palsy, a distinctive pattern of partial third nerve palsy in which weakness is limited to the superior rectus and

A

levator muscles. A brain MRI with attention to the cavernous sinus showed no cause for third nerve palsy and a lumbar puncture was also normal.

What is the anatomic significance of a superior division palsy?

The third nerve exits the midbrain and passes anteriorly through the subarachnoid cistern where it lies in close proximity to a number of vascular structures. The nerve then pierces the dura near the top of the clivus to enter the cavernous sinus. Just before entering the orbit via the superior orbital fissure, the third nerve splits into two divisions: a superior division containing motor fibers to the superior rectus and levator, and an inferior division containing the remaining motor fibers plus the parasympathetic fibers to the iris sphincter and ciliary body. Based on this anatomy, a divisional third nerve palsy should localize to the anterior cavernous

B

38Chapter 2: Orbital disease or neurologic disease?

sinus or superior orbital fissure where the nerve splits. There are, however, well-documented cases in which a divisional palsy was caused by a lesion more proximal in the course of the nerve, indicating that this topographic division occurs earlier in its course. Nevertheless, when imaging a patient with a superior division palsy, attention should be directed initially to the anterior cavernous sinus and superior orbital fissure. If no abnormality is found, the scope of the radiographic investigation should be enlarged to ensure that the rest of the third nerve pathway has been adequately imaged.

The investigation thus far has revealed no intracranial pathology. How would you proceed?

Further questioning revealed that the patient’s pain was decidedly worse with eye movement, particularly on upgaze. Based on this additional history, orbital disease was suspected and a dedicated orbital MRI was obtained, which showed abnormal enhancement and enlargement of the left superior rectus/levator complex (Figure 2.15). Evaluation for inflammatory, infectious, granulomatous and neoplastic etiologies was unrevealing. She was diagnosed with orbital myositis, a localized form of idiopathic orbital inflammatory syndrome, and treated with oral prednisone. Within two days she experienced complete relief of pain, and by one week later her diplopia had resolved completely. The patient was weaned off steroids over the next eight weeks, and she has had no recurrence in six years.

Discussion: Idiopathic orbital inflammatory disease, also referred to as orbital pseudotumor, is a non-granulomatous inflammation of orbital structures with no known local or systemic causes. It may arise in any age group, though most commonly affects young and middle aged adults. Clinical manifestations vary according to the location, severity and duration of the inflammatory process, and clinical subtypes can be defined by the predominant

Figure 2.15 Orbital MRI of the above patient. A coronal post-contrast, fat-suppressed T1-weighted image through the mid-orbit shows enlargement and enhancement of the superior rectus/levator muscle complex on the left side (arrow).

site of involvement. These include dacryoadenitis (lacrimal gland), myositis (one or more extraocular muscles), scleritis, optic perineuritis, mass-like lesions at the orbital apex and diffuse infiltrative inflammation.

Pain is the most common feature of idiopathic orbital inflammation and is the symptom that usually prompts patients to seek medical attention. Those with extraocular muscle involvement also experience diplopia. Accompanying signs of orbitopathy such as periorbital edema, lid swelling, conjunctival injection, proptosis and chemosis are present in most patients. In the patient under discussion, myositis was limited to the superior rectus/levator complex. Because of the very focal nature of the inflammation in this case, typical orbital findings were absent, thus leading to the mistaken impression of a partial third nerve palsy due to intracranial disease. Pain in orbital inflammatory disease can be quite severe and is typically exacerbated by eye movement. This feature is particularly helpful for directing attention to the orbit

as the site of the disease process. Some intracranial processes, such as meningitis, can be associated with pain on eye movement, but in such cases the pain is usually bilateral and accompanied by headache.

The diagnosis of orbital inflammatory disease is usually based on a combination of the clinical and neuro-imaging findings. A post-contrast MRI with coronal views and fat suppression is the preferred study, but in many cases a post-contrast orbit CT can suffice as well since the key findings are essentially the same on both. In orbital myositis, the chief finding is enlargement of one or more extraocular muscles. The tendons are frequently thickened, leading to a tubular configuration of muscle enlargement which is in contrast to the spindle-shaped muscle enlargement characteristic of Graves’ orbitopathy (Figure 2.16). In some patients with orbital pseudotumor, there is also streaky enhancement of the orbital fat or enlargement of the lacrimal gland, and these findings are helpful for confirming the diagnosis. While these differences are helpful for distinguishing these two entities radiographically, the typical clinical presentation of orbital pseudotumor with acute pain is so

different from the insidious, non-painful presentation of Graves’ disease that the two disorders are readily distinguished on clinical grounds in most cases.

Idiopathic orbital inflammatory syndrome is a diagnosis of exclusion, requiring a thorough evaluation for systemic inflammatory disorders (Table 2.1). A biopsy is not considered necessary for the diagnosis if the history, radiographic findings and response to steroids fit the disease profile. Biopsy is reserved for patients with atypical clinical findings, lack of steroid responsiveness, persistent radiographic abnormality despite treatment and in some cases with recurrence following treatment.

Occasional patients with mild forms of idiopathic orbital inflammation can be managed with nonsteroidal anti-inflammatory agents, but in most cases corticosteroids are the mainstay of treatment. Oral (as opposed to intravenous) steroids are usually sufficient and the response is typically dramatic, particularly the resolution of pain within 24–48 hours. Most patients respond well to oral prednisone 60–100 mg daily for two weeks with a slow taper thereafter. Despite this positive initial