Postlesional vestibular reorganization improves the gain but impairs the spatial tuning of the maculo-ocular reflex in frogs. (1/6)

The ramus anterior (RA) of N.VIII was sectioned unilaterally. Two months later we analyzed in vivo responses of the ipsi- and of the contralesional abducens nerve during horizontal and vertical linear acceleration in darkness. The contralesional abducens nerve had become responsive again to linear acceleration either because of a synaptic reorganization in the vestibular nuclei on the operated side and/or because of a reinnervation of the utricular macula by regenerating afferent nerve fibers. Significant differences in the onset latencies and in the acceleration sensitivities allowed a separation of RA frogs in a group without and in a group with functional utricular reinnervation. Most important, the vector orientation for maximal abducens nerve responses was clearly altered: postlesional synaptic reorganization resulted in the emergence of abducens nerve responses to vertical linear acceleration, a response component that was barely detectable in RA frogs with utricular reinnervation and that was absent in controls. The ipsilesional abducens nerve, however, exhibited unaltered responses in either group of RA frogs. The altered spatial tuning properties of contralesional abducens nerve responses are a direct consequence of the postlesional expansion of signals from intact afferent nerve and excitatory commissural fibers onto disfacilitated 2nd-order vestibular neurons on the operated side. These results corroborate the notion that postlesional vestibular reorganization activates a basic neural reaction pattern with more beneficial results at the cellular than at the network level. However, given that the underlying mechanism is activity-related, rehabilitative training after vestibular nerve lesion can be expected to shape the ongoing reorganization.  (+info)

Eye problem following foot surgery--abducens palsy as a complication of spinal anesthesia. (2/6)

BACKGROUND: Paralysis of abducens nerve is a very rare complication of lumbar puncture, which is a common procedure most often used for diagnostic and anesthetic purposes. CASE REPORT: A 38-year-old man underwent surgery for a left hallux valgus while he was under spinal anesthesia. On the first postoperative day, the patient experienced a severe headache that did not respond to standard nonsteroidal anti-inflammatory medication and hydration. During the second postoperative day, nausea and vomiting occurred. On the fourth postoperative day, nausea ceased completely but the patient complained of diplopia. Examination revealed bilateral strabismus with bilateral abducens nerve palsy. His diplopia resolved completely after 9 weeks and strabismus after 6 months. CONCLUSION: Abducens palsy following spinal anesthesia is a rare and reversible complication. Spinal anesthesia is still a feasible procedure for both the orthopaedic surgeon and the patient. Other types of anesthesia or performing spinal anesthesia with smaller diameter or atraumatic spinal needles may help decrease the incidence of abducens palsy. Informing the patient about the reversibility of the complication is essential during the follow-up because the palsy may last for as long as 6 months. Special attention must be paid to patient positioning following the operation. Recumbency and lying flat should be accomplished as soon as possible to prevent cerebrospinal fluid leakage and resultant intracranial hypotension. This becomes much more important if the patient has postdural puncture headache.  (+info)

Traumatic retroclival epidural hematoma in a child: case report. (3/6)

An 11-year-old girl presented with a very rare traumatic retroclival epidural hematoma manifesting as bilateral abducens nerve palsy, deviation of the uvula to the left, and weakened movement of tongue, which developed after a motor vehicle accident. The patient was treated conservatively and showed good outcome. Retroclival hematoma is a mainly pediatric entity usually associated with ligamentous injury at the craniocervical junction, and can be treated conservatively with good outcome.  (+info)

Transient diplopia in dental outpatient clinic: an uncommon iatrogenic event. (4/6)

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Delayed-onset bilateral abducens paresis after head trauma. (5/6)

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Sixth cranial nerve palsy following closed head injury in a child. (6/6)

A five year old female had an isolated abducens nerve palsy following closed head injury. There was no associated skull fracture, haematoma, or other cranial nerve injury. The significance, frequency, and differential diagnosis of traumatic sixth cranial nerve injury is discussed, particularly in paediatric patients. Management is symptomatic; occlusion with an eye pad may be used if diplopia is significant. In young children alternate day occlusion of each eye will help prevent amblyopia. Most cases improve within three months and many resolve by six months. Residual palsy at six months is likely to be permanent and surgical treatment may be needed.  (+info)