Jonathan D. Trobe

Optic Nerve Involvement in Dysthyroidism

Although its prevalence in dysthyroidism is estimated at less than 5%, optic neuropathy should be recognized as a preventable cause of disabling visual loss. Obscured by more obvious external congestive signs, it is usually insidiously progressive and bilateral, but may be acute and unilateral. Neuro-ophthalmic findings are nonspecific (prechiasmal field defects, normal or swollen nerveheads), and the diagnosis should be suspected in the context of typical adnexal changes of dysthyroidism. Optic nerve involvement is probably secondary to apical orbital compression by congested muscles. Treatment with oral corticosteroids, irradiation, or orbital decompression has been beneficial, especially in the early phases.

An Evaluation of the Accuracy of Community-Based Perimetry

We assessed the accuracy of five office-based perimetric technicians in the examination of 14 patients with prechiasmal and chiasmal defects unknown to them. A pre-test followed by two days of instruction and supervised practice; the technicians were then retested on the same patients (post-test). An independent evaluator scored their results. The identification of any field defect rose significantly (P = .039) from 69% in the pre-test to 95% in the post-test. The identification of the hemianopic configuration of a defect rose from 45% in the pre-test to 84% in the post-test (P = .11); initial identification of nasal steps was 77%, falling to 67% in the post-test. Adequate definition of extent, depth, and slope of defects was rare (5%) on the pre-test, but rose significantly (P = .032) to 57% on the post-test. The monitored patient examinations were essential for correcting recurrent flaws in technique. This study shows that such teaching efforts, including emphasis on identifying hemianopic defects, are necessary to raise visual field examination to the level of a consistently reliable diagnostic determinant.

Bilateral optic canal meningiomas: a case report.

In the case presented, bilateral optic canal meningiomas produced binocular visual loss. Correct diagnosis was delayed because of inadequate and misinterpreted radiological studies. Careful radiological and surgical examination of the planum sphenoidale later suggested this as the source of both canalicular masses. The pertinent aspects of this case are reviewed in relation to information from similar cases reported previously. In the future, increased clinical suspicion and more accurate neuroradiological studies should improve the detection and afford earlier surgical treatment of meningiomas of the optic canal.

Perichiasmal Tumors: Diagnostic and Prognostic Features

A review of 49 tumors compressing the intracranial optic nerve, optic chiasm, or optic tract revealed that the majority of patients had symptoms and signs of visual loss predominantly affecting one eye. Seventy-seven per cent of patients had a relative afferent pupillary defect (RAPD), and 96% had a hemianopic defect in at least one eye. All patients had either a RAPD or a hemianopic defect. The junctional pattern of visual field defects was nearly as common (39%) as the classic bitemporal pattern (46%). Many fields contained a mixture of nerve fiber bundle and hemianopic defects; the hemianopias tended to obscure the coexisting nerve fiber bundle defects. Poor preoperative acuity predicted a relatively poor postoperative acuity, but 95% of the patients had 20/40 or better acuity in at least one eye after operation.

The evaluation of horner syndrome.

In this issue of the Journal of Neuro-Ophthalmology, Almog et al (1) present the results of their review of 52 adults referred for outpatient or inpatient consultation to a neuro-ophthalmologist for evaluation of Horner syndrome. They found that in two-thirds of patients, the cause of the Horner syndrome will already be known at the time of the first neuro-ophthalmic consultation (usually surgery or trauma to the head, neck, or chest, dorsolateral medullary stroke, or carotid dissection). Among one-sixth of the patients in whom the cause of Horner syndrome is not yet known, there will be clinical clues to allow localization of the lesion, such as acute neck or face pain (cervical region), arm pain or weakness (brachial plexus or paraspinal region), or sixth cranial nerve palsy (cavernous sinus); in those patients, targeted imaging will usually find the lesion. In the remaining one-sixth of patients, there will be no localizing clues for the Horner syndrome; in those patients, nontargeted imaging of the head, neck, and chest will rarely find a responsible lesion (only 1 case of thyroid carcinoma). This ‘‘real world’’ study, together with previous studies, provides valuable guidance in the evaluation of Horner syndrome in adults and suggests the following approach: Step 1. Confirm that there really is a Horner syndrome. The clinical features—ptosis and miosis—are calling cards, but they may be exceedingly subtle or transient (2). (The report of anhydrosis or absent facial flushing is helpful but rarely elicited.) Because there are other causes of miosis and ptosis (3), topical pharmacologic testing should be used—and results may be positive even if signs are equivocal or completely absent (2)! Cocaine has been the traditional agent, but it is a weak pupil dilator and, as a controlled substance, often is not readily available. It has been supplanted by topical 0.5% apraclonidine (4) (except in children younger than 1 year of age, in whom it may cause serious acute dysautonomia [5,6]), although wider experience will be needed to establish how reliable it is, especially in an acute Horner syndrome (7,8). The traditional use of pharmacologic agents such as topical hydroxyamphetamine to assist in localization is a waste of time. These agents are difficult to obtain and do not provide information reliable enough to allow targeted imaging (9). Step 2. Determine whether there has been previous accidental or surgical trauma to the neck, upper spine, or chest that will explain the Horner syndrome. (Include carotid endarterectomy/stenting and epidural anesthesia among legitimate causes [10,11].) If so, no further diagnostic work-up is necessary. Move to. . . Step 3. Determine whether there are localizing clinical features for the Horner syndrome. For example, ataxia and nystagmus would suggest a medullary lesion. Arm pain/weakness/numbness or myelopathic features would direct attention to the lung apex, brachial plexus, and cervical spine. Acute neck or face pain would direct attention to the cervical carotid artery. (The oculosympathetic fibers crawling up the outside of the cervical carotid artery are exquisitely vulnerable to compression, trauma, dissection, and inflammation, including arteritis.) Beware of attributing persistent Horner syndrome to trigeminal autonomic syndromes such as cluster headache; carotid artery dissection can perfectly mimic these syndromes (12). Ear pain or hearing loss would direct attention to the temporal bone and carotid canal (13). Ipsilateral sixth cranial nerve palsy would direct attention to the cavernous sinus. Perform targeted (selective) imaging on the basis of this kind of information. If there are no localizing features, then the Horner syndrome is considered ‘‘isolated,’’ and you move to. . . Step 4. Perform nontargeted (nonselective) imaging of the upper chest and neck as far up as the skull base to encompass the second (preganglionic) segment and the extracranial part of the third (postganglionic) segment of the oculosympathetic pathway. If the Horner syndrome is truly ‘‘isolated,’’

Clinical Neuropathology: Text and Color Atlas

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Diagnostic strategies in the management of unexplained visual loss. A cost-benefit analysis.

In the investigation of visual loss from anterior visual pathway disease, it is imperative to differentiate the infrequent compressive from the much more common noncompressive lesions. To determine how relatively low-cost, risk-free, but error-prone visual field examination (VF) and high-cost, risk-prone, but accurate CT Scan (CT) and cerebral angiography (Angio) can be cost-effectively utilized to solve this diagnostic problem, the authors have developed a decision making model for the analysis of three management strategies. The visual field examination precedes and determines the use of neuroradiologic studies in Strategy A (VF-CT-Angio), whereas it follows the neuroradiologic studies in Strategies B (CT-VF-Angio) and C (CT-Angio-VF). The visual field-determined strategy (A) proved most cost-effective, based upon an estimated 6% or lower relative prevalence of chiasmal compressive lesions, a negligible risk in delaying their diagnosis, and a sensitive method of visual field examination. At a visual field sensitivity to chiasmal defects of 84% and a specificity of 88%, Strategy A annually saves

Ophthalmic artery occlusion secondary to radiation-induced vasculopathy

4 million over Strategy B and

Facial and trigeminal neuropathies in cavernous sinus fistulas

27 million over Strategy C. At lower levels of perimetric accuracy, Strategy B is the most cost-effective approach. Strategy C is never cost-effective.

Doctor:patient communication in ophthalmic outpatient visits.

A 35-year-old man with neurofibromatosis type 1 (NF1) had a left ophthalmic artery occlusion that caused no light perception OS 28 years after having been treated with external beam radiation therapy for a presumed glioma of the right optic nerve and chiasm. Clinical and imaging findings were consistent with radiation-induced cerebral vasculopathy. This ophthalmic complication has never been reported, despite the common occurrence of severe carotid-ophthalmic artery junction stenosis after radiation in NF1 patients. Even though modern radiation techniques limit collateral damage, this modality should be used with discretion in NF1 patients, given the vulnerability of their immature cerebral vasculature to radiation.