Ulf Havelius

II. Improved dark adaptation after carotid endarterectomy : Evidence of a long-term ischemic penumbra?

We have reported that dark vision is impaired in symptomatic carotid artery disease and that the impairment correlates with internal carotid artery stenosis. To find out whether this impairment is reversible after carotid endarterectomy, dark adaptation was examined pre- and postoperatively. Twenty-one consecutive patients were examined by dark adaptometry. Two examinations were done for each eye on two consecutive days pre- and postoperatively. Thirty-one matched control subjects were examined under identical conditions. The control subjects did not have clinical evidence of carotid artery disease. Patients and control subjects were free of ophthalmologic disorders. Dark vision frequently improved remarkably after endarterectomy. The average retinal sensitivity to light in darkness on the operated side doubled, and there was also improvement on the nonoperated side. There was no significant change in dark vision in the control subjects, negating a learning effect. The findings suggest the existence of reversible neuronal ischemia secondary to hemodynamic causes or frequent subclinical microembolization. Because the circulatory conditions are optimized, formerly inactive, surviving neurons may regain function.

Minor vessels leaving the extracranial internal carotid artery Possible clinical implications

The microvascular anatomy of the internal carotid artery (ICA) was studied in a consecutive autopsy material consisting of 72 carotid arteries from 36 individuals. In 13 IC As from 10 individuals 14 minor arteries with a calibre of 65 to 165 μm were found to leave the extracranial ICA lumen within 31 mm from the base of the skull. These vessels may contribute to the blood supply of the periadventitious sympathetic nerve plexus and explain the occurrence of a Horners syndrome in disease of the ICA. Perhaps these vessels may also be relevant in the pathophysiology of unilateral deficits of lower cranial nerves with an acute onset.

Reversibility of neurological deficits in vitamin B12 deficiency

SummaryA female patient with subacute neurological deficits secondary to an hereditary vitamin B12 deficiency was repeatedly examined clinically and neurophysiologically. It is concluded that neurological normalization after treatment with vitamin B12 also occurs within the CNS. Such normalization takes place soon after initiating treatment and probably reflects other neuronal mechanisms than remyelination, i.e. recovery from conduction block in fast somatosensory pathways and/or improvement of synaptic transmission.

The Enhanced Ciliospinal Reflex in Asymptomatic Patients With Cluster Headache is Due to Preganglionic Sympathetic Mechanisms

An amplified ciliospinal reflex response has been documented in patients with cluster headache, lacking a Horner like syndrome. The mechanism is unknown, Tentatively, it may be due to an increased release of monoamines from post‐ganglionic sympathetic nerve endings or an increased density of postsynaptic adrenergic receptors in the dilatator muscle of the iris.

Minor arteries from the intrapetrosal internal carotid artery: Possible clinical implications. An anatomical study

The microvascular anatomy of the petrosal and suprapetrosal segments of the internal carotid artery (ICA) was studied in a consecutive autopsy material consisting of 58 ICAs from 29 individuals and in an additional 11 decalcified tissue blocks of the pars petrosa. The level above the external orifice of the carotid canal and the lumen width were registered for every artery debranching from the ICA. Special attention was paid to topographical close relationships between carotid branches and sympathetic nerves indicating a possible nutritional significance for the small arteries. The petrosal ICA had one or more branches in 64% of the specimens. 90% of the individuals had at least one branch from either ICA. The branches showed a mean lumen width of 187 μm for the petrosal and 290 μm for the suprapetrosal segment of the ICA. A considerable number of the petrosal carotid branches probably represent vasa nervorum for the sympathetic nerves and have a specific histological appearance. These vessels may have c...

Dark Adaptation during Systemic Hypoxia Induced by Chronic Respiratory Insufficiency

PURPOSE To investigate dark adaptation during hypoxia in patients with chronic respiratory failure. METHODS At three visits, dark adaptation was recorded by computerized dark adaptometry in 13 patients with chronic respiratory insufficiency treated by long-term oxygen therapy. At visits 1 and 3, the patients were administered their usual oxygen supplement. At visit 2, no oxygen was given. At each visit, an analysis of arterial blood gases measured pH, partial pressure of O(2) (Pao(2)), partial pressure of CO(2) (Paco(2)), base excess (BE), standard bicarbonate (HCO(3)), and arterial oxygen saturation. Pulse oximetry (POX) was also recorded. RESULTS Significant differences were recorded between visits 1 and 2 and between visits 2 and 3 for Pao(2), arterial oxygen saturation, and POX; no differences were found for pH, Paco(2), BE, or HCO(3). No differences were seen between visits 1 and 3 for any of the laboratory parameters. All patients had normal and unchanged dark adaptation at the three visits. CONCLUSIONS Hypoxia in chronic respiratory insufficiency was associated with normal dark adaptation, in contrast to hypoxia in healthy persons at high altitudes, which is known to produce impaired dark adaptation. The result may partly reflect the influence of Paco(2) on the lumen of choroidal and retinal vessels. At high altitudes, with hypocapnic vasoconstriction the oxygen supply to the retina is further compromised, resulting in reduced dark adaptation. The authors hypothesize that respiratory insufficiency with hypercapnia or normocapnia will have larger choroidal and retinal vessel lumens, added to by further dilation of retinal vessels during hypoxia. The tentative net effect would be preserved dark adaptation.

Two Eyes Are Better Than One—Binocular Summation of Dark Vision in Healthy Individuals and Patients with Chronic Respiratory Disease

Abstract We compared monocular and binocular absolute thresholds of dark adaptation in two separate study populations. Eighteen healthy individuals (Group A) and 13 patients with chronic respiratory insufficiency (Group B) were examined three times each by computerised dark adaptometry with simultaneous but separate recordings from each eye and binocularly. The respiratory patients received oxygen supplement at visits 1 and 3. In Group A, at all three visits, binocular dark adaptation was significantly more sensitive (40.5%) than monocular dark adaptation with either eye. In Group B, at visits 1 and 3, binocular dark adaptation was also significantly more sensitive than monocular dark adaptation (40.5% higher than the right and 47% higher than the left eye). However, in Group B, at visit 2 without oxygen treatment, no significant differences were observed between monocular and binocular sensitivities. Binocular dark vision was superior to monocular dark vision in healthy individuals and in patients with respiratory insufficiency that were provided oxygen supplementation. Furthermore, deficit in oxygen seems to affect binocular summation, perhaps by impaired enhancement in the central nervous system.