Visually Evoked Potentials in a Patient with a Fyodorov-Zuev Keratoprosthesis

Purpose: To describe a visually evoked potential (VEP) examination performed on a patient with a keratoprosthesis. Methods: We report the case of a 60-year-old patient with a Fyodorov-Zuev keratoprosthesis in the right eye complained of gradual visual deterioration in that eye. His past medical history consisted of failed corneal graft procedures due to corneal dystrophy and an Ahmed valve implantation due to secondary glaucoma. A clinical examination and an ultrasound demonstrated vitreal opacities. In order to assess the visual status, a flash VEP test was conducted. Results: VEP recorded from the right eye consisted of a broadened and poorly formed positive P1 wave, with a subnormal amplitude, but a normal latency. Consequently, the patient underwent a pars plana vitrectomy. Conclusion: This case demonstrates the viability of VEP exams in patients with keratoprostheses.

Outcome measures for trials of remyelinating agents in multiple sclerosis: retrospective longitudinal analysis of visual evoked potential latency

Objective Visual evoked potentials (VEP) may be suitable surrogate outcome measures in multiple sclerosis (MS) remyelination trials. The extent of spontaneous changes of subclinically delayed VEP is unknown, whereas VEP improve after acute optic neuritis (ON). Methods In all, 124 patients with three VEP recordings at least 3 months apart: 71 patients with MS who had never suffered clinical ON; 53 patients with ON (isolated ON or ON as an attack of MS at first recording). Latencies of P100 were analyzed by multivariate analysis of variance. Results Eyes of patients with MS had a mean P100 latency of 110.2 ms, worsening mildly over time ( n = 104 eyes, P = 0.022). MS patients' eyes with subclinical demyelination (delayed P100 latency at first recording >116 ms) showed no significant evidence of remyelination ( n = 24 eyes, P = 0.27). By contrast, in ON patients' affected eyes, mean P100 latency decreased ( P = 0.001), whereas unaffected eyes remained stable ( P = 0.26). Clinically non-affected eyes from both diagnostic groups with subclinically prolonged latencies remained stable ( n = 32: mean P100 at 124.8 ± 10.7, 123.5 ± 13.6, and 122.8 ± 13.1 ms; P = 0.57), whereas non-affected eyes with normal latency at baseline deteriorated slightly ( P = 0.001). A subgroup with more homogeneously defined follow-up periods confirmed this observation. Non-affected eyes selected for stability (difference <5 ms) between first and second recording deteriorated (normal baseline, n = 66 eyes, P = 0.013) or remained stable (prolonged baseline, n = 18 eyes, 95% confidence interval of change –5.42 to +6.89 ms, P = 0.805). Conclusion Prolonged P100 latencies in eyes never affected by clinical ON remain stable and thus can be used as surrogate outcome measure for remyelination trials.

Physiologic studies of male sexual dysfunction in multiple sclerosis

Objective: We conducted this investigation to better define the neural disruptions that result in sexual dysfunction in men with multiple sclerosis (MS), using genital electrodiagnostic testing and nocturnal penile tumescence and rigidity monitoring. Methods: Thirteen men with MS and sexual dysfunction were recruited for the study. Twelve healthy, sexually potent men were enrolled as controls. All underwent pudendal somatosensory evoked potential (SEP) testing using standard methods, and a new modification to isolate the right and left dorsal nerves of the penis. RigiScan testing was performed on the MS subjects to assess nocturnal erectile function. Results: Unilateral and bilateral DNP SEPs were able to be performed on the control subjects. In all but one MS subjects, DNP SEP abnormalities were found. Three men had normal latency bilateral DNP SEP latencies, but on unilateral DNP testing, abnormalities were identified. Seven men, including those with abnormal or absent SEP latencies, had normal nocturnal erectile activity. There was no correlation between overall functional status, presence of abnormal or absent SEP, and quality of nocturnal erectile activity. Conclusions: Genital SEP abnormalities are common in men with MS and sexual dysfunction. Unilateral DNP SEP testing was more sensitive in identifying abnormalities than the standard method of pudendal SEP testing. One of the causes of sexual dysfunction in men with MS may be due to genital somatosensory pathway disruption, with sparing of the efferent tracts in some men.

Organization of sequential typing movements

1. Experienced touch typists were asked to type words that contained only one or two letters typed by one of the two hands. When a word contained a pair of letters typed by one hand, the letters could be consecutive, or there could be one, two, or three intervening letters typed with the other hand. 2. We studied cases in which pairs of letters were either identical, different but typed with the same finger, or typed with two different fingers on the same hand. 3. Translational and rotational motion of the fingers and wrist was computed optoelectronically from the location of reflective markers on the hands. Finger and wrist motion recorded when subjects typed pairs of letters was compared with the motion recorded when the subject typed either letter in isolation. 4. When the subject typed the same letter consecutively, or separated by intervening letters, the second keystroke began only after the first key had been pressed. The same result was obtained when the second letter was not identical but was typed with the same finger. Up to the time of the first keypress, the initial keystroke kinematics were identical to those for that letter typed in isolation. 5. When the second letter in a pair was typed with the use of a different finger, the initial focal movement (wrist and finger striking the key) was unaffected up to the time of initial keypress. However, the second finger could begin to move toward the second key shortly before the initial keypress, and therefore the corollary movements normally involved in the initial keystroke were affected. 6. These results indicate that typing movements are executed primarily in a serial fashion, letter by letter. There can be some overlap between consecutive keystrokes only if they are executed with different fingers. 7. Words in which two letters typed with one hand were separated by three letters typed with the other hand provided subjects the opportunity to initiate the second keystroke at a range of times after the first keypress. 8. When the second letter differed from the first, subjects always returned to the home position after the first keypress and initiated the second keystroke with a normal latency. However, when the second letter was the same as the first letter, subjects sometimes suppressed the return to the home position after the first keystroke and maintained their finger poised over the key. 9. Thus keystrokes of one hand are best described as being executed sequentially. However, the findings presented here also indicate that movement planning encompasses strings of letters.

Relationship between visual evoked potentials and intracranial pressure

✓ The relationship between intracranial pressure (ICP) and latency of visual evoked potentials (VEP) was investigated in hydrocephalic patients with suspected shunt malfunction and in patients with severe head trauma. A positive correlation of increase in latency of wave N2 (normal latency 71 ± 9.2 msec) of the VEP with elevations in ICP was observed. A potential role for VEP in both the assessment of shunt function and the monitoring of patients with severe head injury is suggested by these findings.

Effect of a transitory ischaemia on the structure-linked latency of rat liver acid phosphatase and β-galactosidase

The structure-linked latency of acid phosphatase and beta-galactosidase was studied in rat liver lobes made ischaemic for 1 or 2 h and then recirculated with blood for increasing periods. Free activity of acid phosphatase and unsedimentable activity of beta-galactosidase are increased in homogenates of ischaemic livers. When ischaemia had been maintained for 1 h, the recovery of normal latency for both enzymes was observed 1 h after re-establishment of the blood flow. After a 2 h period of ischaemia, unmasked activity markedly decreases during the first 1 h after restoration of blood flow; after that, a large and irreversible secondary rise takes place. Chlorpromazine, injected 30 min before or just after induction of ischaemia, extensively prevents the latency decrease occurring during restoration of blood flow. Modifications of the hydrolase distribution pattern obtained after differential centrifugation are in agreement with the latency changes. These results suggest that a 2 h ischaemia causes an alteration of the liver lysosomes that is largely reversible and that restoration of blood flow induces an irreversible alteration of these organelles. Chlorpromazine treatment prevents the irreversible lesion from taking place.

Monitoring optic nerve function during craniotomy

✓ During surgical removal of a pituitary adenoma, conduction in the anterior visual pathways was monitored by continuous recording of visual evoked responses (VER). The method employed a scleral contact lens with an embedded flashing diode for delivery of visual stimuli. Evoked potentials of nearly normal latency, amplitude, and form were recorded from occipital scalp electrodes immediately after the optic nerves were decompressed. Restoration of the VER was correlated with restoration of normal vision.