Klara Landau

Single motor unit activity in human extraocular muscles during the vestibulo‐ocular reflex

•  While the eye movements have been well characterized during the vestibulo‐ocular reflex, the corresponding motor unit activity in human eye muscles is not well understood. •  The present study describes the first single motor unit recordings during the vestibulo‐ocular reflex in human eye muscles. •  Simultaneous needle and surface recordings identified the inferior oblique as the eye muscle of origin of the ocular vestibular evoked myogenic potential (oVEMP), thus validating the physiological basis of this clinical test of otolith function. •  The results demonstrate short‐latency vestibulo‐ocular projections from the otoliths to individual eye muscles. •  Single motor unit activity of eye muscles provides a window into neural activity of the ocular motor nuclei in humans.

PITUITARY APOPLEXY: RE-EVALUATION OF RISK FACTORS FOR BLEEDING INTO PITUITARY ADENOMAS AND IMPACT ON OUTCOME

OBJECTIVE To assess frequency, symptoms and outcome of pituitary apoplexy (PA) among pituitary adenoma patients, to gain better insight into risk factors for bleeding into pituitary adenoma and to estimate the sequelae of PA by means of a matched control group. METHOD By reviewing charts of 574 patients with pituitary adenoma, we analysed incidence, symptoms and outcome of PA and potential risk factors for developing PA by means of a control group (patients with pituitary adenoma without PA). RESULTS In total, 42 suffered from PA, all had macroadenomas; 30/217 male (14%) and 12/179 female (7%) macroadenoma patients, 32/194 patients with clinically non-functioning (16.5%) and 10/202 with clinically active (5.0%) macroadenoma were affected. Antithrombotic therapy predisposed patients to PA (P=0.026), diabetes mellitus and hypertension did not (P=1.00). Patients with PA and pituitary adenoma patients without PA had similar frequencies of hypopituitarism (45 vs 48%, P>0.05) and visual field defects (38 vs 55%, P>0.05), but ophthalmoplegia was significantly more common (76 vs 5%, P<0.001) in patients with PA. Nearly all patients were treated by surgery; most recovered from ophthalmoplegia, whereas visual function improved only moderately. Endocrine outcome was worse in patients with PA than in patients without PA. CONCLUSIONS Male sex and characteristics of the adenoma itself (especially tumour size and tumour type) rather than patients cardiovascular risk factors such as diabetes and hypertension seem to predispose to PA; antithrombotic therapy may also be important.

Tolosa-Hunt syndrome: MR imaging features in 15 patients with 20 episodes of painful ophthalmoplegia

PURPOSE (a) To assess MR features in patients with Tolosa-Hunt syndrome (THS) and to (b) correlate MR findings with criteria derived from previously reported pathologic observations. METHODS Fifteen patients with twenty episodes of painful ophthalmoplegia prospectively selected according to International Headache Society (IHS) standards underwent MR examinations focused on the cavernous sinus. Initial examinations in 20 and follow-up MR images in 17 episodes were retrospectively reviewed by 3 independent observers. RESULTS The primary criteria: an enhancing soft tissue lesion within the cavernous sinus, increase in size and lateral bulging of the anterior cavernous sinus contour were consistently present in 15 initial episodes and in 5 recurrences (20/20). Agreement among observers was 100%. The secondary criteria: internal carotid artery narrowing in 7 patients, extension towards the superior orbital fissure in 13 and orbital apex involvement in 8 patients were unanimously agreed upon in 87.5%, 86.6% and 80%. Complete resolution of findings was observed on follow-up studies. CONCLUSION In patients with THS the MR features conform to previously reported pathologic findings. MR features are evocative of THS when an increase in size and bulging of the dural contour of the anterior CS supplemented by carotid artery involvement and extension towards the orbit are present. Resolution of findings within 6 months is required to support the diagnosis.

Optical Coherence Tomography Findings in Shaken Baby Syndrome

PURPOSE To evaluate features of optical coherence tomography (OCT) associated with Shaken Baby syndrome (SBS) in an attempt to gain new insight into the pathophysiology of this phenomenon. DESIGN Institutional prospective observational case series. METHODS We report three infants with SBS. Each patient underwent an ophthalmic examination including slit-lamp biomicroscopy, dilated indirect ophthalmoscopy, color fundus photography, and OCT. RESULTS In all infants, numerous bilateral multilayered retinal hemorrhages were present. In one case, bilateral perimacular folds had occurred. OCT confirmed retinal hemorrhages and perimacular folds. Moreover, OCT revealed vitreoretinal traction in all infants and suspected hemorrhagic macular retinoschisis in one case. Based on OCT findings, a hypothesis of vitreoretinal traction development and retinal fold formation is proposed. CONCLUSIONS OCT provided valuable additional information about the ocular pathology in patients with SBS. Vitreoretinal membrane formation seen in OCT could support the pathophysiological theory of a direct mechanical effect. OCT revealed preretinal blood accumulation as a cause for localized vitreous detachment and vitreoretinal traction. Furthermore, OCT showed persistent attachment of the vitreous to the internal limiting membrane at the apices of perimacular folds and suggested small hemorrhagic macular retinoschisis in one patient. Perimacular folds and hemorrhagic macular retinoschisis are regarded as highly specific for SBS and indicate poor visual outcome. Thus OCT might be of both diagnostic and prognostic value in SBS.

New insights into ocular blood flow at very high altitudes

Little is known about the ocular and cerebral blood flow during exposure to increasingly hypoxic conditions at high altitudes. There is evidence that an increase in cerebral blood flow resulting from altered autoregulation constitutes a risk factor for acute mountain sickness (AMS) and high-altitude cerebral edema (HACE) by leading to capillary overperfusion and vasogenic cerebral edema. The retina represents the only part of the central nervous system where capillary blood flow is visible and can be measured by noninvasive means. In this study we aimed to gain insights into retinal and choroidal autoregulatory properties during hypoxia and to correlate circulatory changes to symptoms of AMS and clinical signs of HACE. This observational study was performed within the scope of a high-altitude medical research expedition to Mount Muztagh Ata (7,546 m). Twenty seven participants underwent general and ophthalmic examinations up to a maximal height of 6,800 m. Examinations included fundus photography and measurements of retinal and choroidal blood flow, as well as measurement of arterial oxygen saturation and hematocrit. The initial increase in retinal blood velocity was followed by a decrease despite further ascent, whereas choroidal flow increase occurred later, at even higher altitudes. The sum of all adaptational mechanisms resulted in a stable oxygen delivery to the retina and the choroid. Parameters reflecting the retinal circulation and optic disc swelling correlated well with the occurrence of AMS-related symptoms. We demonstrate that sojourns at high altitudes trigger distinct behavior of retinal and choroidal blood flow. Increase in retinal but not in choroidal blood flow correlated with the occurrence of AMS-related symptoms.

The visual impact of fractionated stereotactic conformal radiotherapy on seven eyes with optic nerve sheath meningiomas.

Background: Treatment of primary optic nerve sheath meningiomas (ONSMs) remains controversial. Although recent studies have suggested a favorable outcome of radiotherapy, controlled data on the efficacy of fractionated stereotactic conformal radiotherapy (SCRT) in primary ONSMs are still lacking. Methods: Seven eyes treated with SCRT (total dose: 54 Gy) were compared with six eyes that were not treated because of patient or physician preference. The indication for intervention was deterioration of visual function with or without imaging evidence of tumor progression. Patients with secondary ONSMs and those with neurofibromatosis type 2 were excluded. The mean follow-up period was 57 months for the treated eyes and 61 months for the untreated eyes. Results: Among the seven treated eyes, visual acuity improved in six, five of which sustained improvement of three or more Snellen lines. One eye deteriorated by two lines. Visual field improved in four eyes, remained stable in two, and deteriorated in one. Four untreated eyes showed worsening of visual acuity and two remained stable. Visual field deteriorated in three eyes and was stable in three. None of the untreated eyes experienced improvement in visual acuity or visual field. No complications of treatment were documented. Conclusions: In agreement with previous reports, these results indicate that SCRT is superior to observation in its impact on visual function in eyes with primary ONSMs.

High Incidence of Optic Disc Swelling at Very High Altitudes

OBJECTIVES To determine the incidence of optic disc swelling as a possible indicator of cerebral edema in a large group of healthy mountaineers exposed to very high altitudes and to correlate these findings with various clinical and environmental factors and occurrence of acute mountain sickness and high-altitude cerebral edema. METHODS This multidisciplinary, prospective, observational cohort study was performed in 2005 within the scope of a medical research expedition to Muztagh Ata (7546 m [24,751 ft]) in Western Xinjiang Province, China. Twenty-seven healthy mountaineers aged 26 to 62 years participated. Medical examinations were performed in Switzerland 1 month before and 4 1/2 months after the expedition. Ophthalmologic examinations were performed at 4 high camps (maximum elevation, 6865 m [22,517 ft]). Optic disc status was documented using digital photography. Further assessments included arterial oxygen saturation and cerebral acute mountain sickness scores. RESULTS Sixteen of 27 study subjects (59%) exhibited optic disc swelling during their stay at high altitudes, with complete regression on return to lowlands. Significant correlation was noted between optic disc swelling and lower arterial oxygen saturation (odds ratio, 0.86 per percentage of arterial oxygen saturation; 95% confidence interval, 0.81-0.92; P < .001), younger age (odds ratio, 0.95 per year; 95% confidence interval, 0.90-0.99; P = .03), and higher cerebral acute mountain sickness scores (odds ratio, 2.32 per 0.1 point; 95% confidence interval, 1.48-3.63; P < .001). CONCLUSION Optic disc swelling occurs frequently in high-altitude climbers and is correlated with peripheral oxygen saturation and symptoms of acute mountain sickness. It is most likely the result of hypoxia-induced brain volume increase.

Anatomy and physiology of the human eye: effects of mucopolysaccharidoses disease on structure and function – a review

The current paper provides an overview of current knowledge on the structure and function of the eye. It describes in depth the different parts of the eye that are involved in the ocular manifestations seen in the mucopolysaccharidoses (MPS). The MPS are a group of rare inheritable lysosomal storage disorders characterized by the accumulation of glycosaminoglycans (GAGs) in cells and tissues all over the body, leading to widespread tissue and organ dysfunction. GAGs also tend to accumulate in several tissues of the eye, leading to various ocular manifestations affecting both the anterior (cornea, conjunctiva) and the posterior parts (retina, sclera, optic nerve) of the eye.

Unilateral swollen disc due to increased intracranial pressure

Truly unilateral papilledema is rare and poses a diagnostic problem. The authors have prospectively looked for patients with truly unilateral papilledema and found 15 patients, 10 of whom had idiopathic intracranial hypertension. Neuroimaging did not indicate a reason for the lack of swelling in the other nerve. The visual deficits and outcomes were similar to those of patients with bilateral papilledema. Although monocular papilledema is uncommon, a lumbar puncture with opening pressure measurement should be considered.

Ophthalmological findings in Joubert syndrome

PurposeJoubert syndrome (JS) is an autosomal-recessive inherited complex malformation of the midbrain–hindbrain. It has been associated with ocular and oculomotor abnormalities. The aim of our study was to extend the ophthalmic knowledge in JS and to add new findings.MethodsIn a retrospective study, 10 consecutive patients, who met the revised diagnostic criteria of JS were included. Mutation analysis was carried out in all the cases. Each patient underwent a comprehensive neuro-ophthalmological examination.ResultsBilateral drusen of the optic disc were found in two patients. Four patients showed bilateral morphological and functional signs of retinal dystrophy (CEP290mutation in two cases and AHI1mutation in one case). In nine patients performance during smooth pursuit, saccades, and vestibulo-ocular reflex (VOR) cancellation was poor.ConclusionsTo the best of our knowledge, the association of optic disc drusen with JS has not yet been described. In support of the earlier findings, decreased smooth pursuit and VOR cancellation, as well as partial-to-complete oculomotor apraxia seem to be the key oculomotor features of JS. Genotype–phenotype correlations showed the predictive value of CEP290and AHI1mutations for retinal involvement.