Failure of pattern recognition

Some neuro-ophthalmic signs and symptoms are non-specific, produced by a variety of disease processes in more than one location within the neuraxis. In certain cases, however, a particular combination of findings can only be due to a disease process in one place. For example, the combination of an ipsilateral optic neuropathy and contralateral superior temporal defect indicates a lesion at the junction of the optic nerve and chiasm, referred to as a “junctional scotoma”. So-called “crossed brainstem syndromes” in which there is an ipsilateral cranial neuropathy and contralateral long tract deficit are another such example. Similarly, the presence of an ipsilateral Horner syndrome and contralateral fourth nerve palsy is exquisitely localizing to an area in the midbrain lateral to the cerebral aqueduct, involving the descending sympathetic fibers and the fascicles from the trochlear nucleus prior to their decussation. In some of these conditions, the responsible lesion is small or otherwise subtle, and in these cases the clinical findings are particularly valuable for pointing to the correct diagnosis. This chapter consists of several such examples in which accurate diagnosis depends on familiarity with these patterns.

Painful ophthalmoplegia

Case: A 35-year-old construction worker developed pain behind the left eye radiating up to the brow and vertex on that side. Several days later he experienced oblique diplopia and drooping of the left upper lid that worsened over several days. Examination

three weeks after onset showed complete left upper lid ptosis and marked external ophthalmoplegia of the left eye, including absence of incyclotorsion on attempted downgaze (Figure 6.1). There was mild anisocoria, left pupil smaller than the right, that was best seen in dim illumination; but both pupils reacted briskly to light stimulation. Afferent visual function was normal. There was decreased sensation to pain and temperature in the distribution of the ophthalmic division of the left trigeminal nerve, as well as a decreased corneal reflex on that side. An MRI was reportedly normal (Figure 6.2), as were the results of a number of blood tests, urinalysis, tuberculosis skin test and chest radiograph.

Where is this patient’s lesion?

This patient presented with painful unilateral ophthalmoplegia. His examination indicated dysfunction of cranial nerves three, four, six, the ophthalmic branch of five, and the oculosympathetics on the left side. This constellation of findings is exquisitely localizing to the region of the cavernous sinus and superior orbital fissure. Though anatomically distinct spaces, there is not a way to distinguish clinically between a lesion of the cavernous sinus and one in the superior orbital fissure, and therefore the constellation of findings that results from a lesion in this area is sometimes referred to as the “sphenocavernous syndrome”. Because so many nerves pass through so small a space, even a very small lesion in this area can produce multiple cranial nerve deficits.

Figure 6.2 MRI of the same patient. This axial post-contrast T1-weighted image was read as normal.

Careful inspection of this patient’s MRI disclosed an abnormal hyperintensity within the superior orbital fissure on post-contrast T1-weighted images (Figure 6.3). Despite the severity of this patient’s clinical findings, the radiographic abnormality was surprisingly subtle. Tests for specific systemic inflammatory disorders were unrevealing and a presumptive diagnosis of Tolosa Hunt syndrome was made. He was treated with high-dose oral prednisone (80 mg per day), which brought prompt relief of his pain. Re-examination one month later showed dramatic improvement of ocular motility with normal trigeminal sensation. He continued a slow taper of his steroids over the next several months, with eventual resolution of his clinical deficits and radiographic abnormality.

Discussion: Tolosa Hunt syndrome is an idiopathic granulomatous inflammatory process involving the area of the cavernous sinus and superior orbital fissure, causing painful ophthalmoplegia. There are no serologic markers for this condition and it is rarely necessary or appropriate to biopsy these structures,

Table 6.1 International Headache Society criteria for the diagnosis of Tolosa Hunt syndrome (Cephalalgia, 24 Suppl 1 (2004))

1.One or more episodes of unilateral orbital pain lasting weeks if untreated

2.Paralysis of one or more cranial nerves three, four, six and/or demonstration of granuloma by MRI or biopsy

3.Paresis coincides with onset of pain or follows it within two weeks

4.Pain and paresis resolve within 72 hours when treated adequately with steroids

5.Other causes have been excluded by appropriate investigations

and thus the diagnosis is typically a clinical one (see Table 6.1).

Tolosa Hunt syndrome (THS) typically presents with acute onset of periorbital or hemi-cranial pain associated with numbness or paresthesias if the trigeminal nerve is involved. In addition, there is ipsilateral paralysis of one or more ocular motor cranial nerves and Horner syndrome in varying combination. In up to 20% of cases the inflammation extends anteriorly to produce optic nerve dysfunction. Involvement of the seventh nerve is an

uncommon manifestation. It is important to recognize that this constellation of findings simply localizes a lesion to the cavernous sinus/superior orbital fissure region and is not specific for THS. The list of diseases that can affect the parasellar region is broad, and a diagnosis of Tolosa Hunt syndrome is one of exclusion after other causes have been ruled out (see Table 6.2).

MR imaging is often abnormal in patients with THS. The contents of the cavernous sinus are usually best assessed by inspection of thin section T1weighted post-contrast views in the coronal plane. In most cases of THS there is enlargement and increased enhancement of the cavernous sinus. When mild, this may appear as loss of the normal concavity of the lateral wall as seen on both coronal and axial images (Figure 6.4). There may also be enhancement of the adjacent dural wall and abnormal soft tissue surrounding and narrowing the cavernous internal carotid artery. In occasional cases there is extension of this abnormal soft tissue into the orbital apex, sphenoid sinus or floor of the middle cranial fossa. However it is important to be aware that in some cases even high quality imaging may be normal. In other cases, a radiographic