Perceptual consequences of disrupted auditory nerve activity.
(49/228)
Perceptual consequences of disrupted auditory nerve activity were systematically studied in 21 subjects who had been clinically diagnosed with auditory neuropathy (AN), a recently defined disorder characterized by normal outer hair cell function but disrupted auditory nerve function. Neurological and electrophysical evidence suggests that disrupted auditory nerve activity is due to desynchronized or reduced neural activity or both. Psychophysical measures showed that the disrupted neural activity has minimal effects on intensity-related perception, such as loudness discrimination, pitch discrimination at high frequencies, and sound localization using interaural level differences. In contrast, the disrupted neural activity significantly impairs timing related perception, such as pitch discrimination at low frequencies, temporal integration, gap detection, temporal modulation detection, backward and forward masking, signal detection in noise, binaural beats, and sound localization using interaural time differences. These perceptual consequences are the opposite of what is typically observed in cochlear-impaired subjects who have impaired intensity perception but relatively normal temporal processing after taking their impaired intensity perception into account. These differences in perceptual consequences between auditory neuropathy and cochlear damage suggest the use of different neural codes in auditory perception: a suboptimal spike count code for intensity processing, a synchronized spike code for temporal processing, and a duplex code for frequency processing. We also proposed two underlying physiological models based on desynchronized and reduced discharge in the auditory nerve to successfully account for the observed neurological and behavioral data. These methods and measures cannot differentiate between these two AN models, but future studies using electric stimulation of the auditory nerve via a cochlear implant might. These results not only show the unique contribution of neural synchrony to sensory perception but also provide guidance for translational research in terms of better diagnosis and management of human communication disorders. (+info)
Maxillary zoster with corneal involvement.
(50/228)
A case, of maxillary zoster with corneal involvement in a young patient is described. Corneal involvement in maxillary zoster (Medline search) is rare. (+info)
Multiple cranial nerve palsy in an HIV-positive patient.
(51/228)
We report the case of a 32 -year- old HIV-positive Indian male who presented with sixth nerve (bilateral), ninth, tenth and twelfth nerve palsies; cerebellar and posterior column involvement. CT scan showed gyriform enhancement in the right occipital lobe and nodular leptomeningeal enhancement in the left frontal lobe. Cytomegalovirus serology was positive and the patient was treated as presumed CMV. HIV can present with multiple cranial neuropathy and varied neurological involvement. (+info)
The wide spectrum of clinical manifestations in Sjogren's syndrome-associated neuropathy.
(52/228)
We assessed the clinicopathological features of 92 patients with primary Sjogren's syndrome-associated neuropathy (76 women, 16 men, 54.7 years, age at onset). The majority of patients (93%) were diagnosed with Sjogren's syndrome after neuropathic symptoms appeared. We classified these patients into seven forms of neuropathy: sensory ataxic neuropathy (n = 36), painful sensory neuropathy without sensory ataxia (n = 18), multiple mononeuropathy (n = 11), multiple cranial neuropathy (n = 5), trigeminal neuropathy (n = 15), autonomic neuropathy (n = 3) and radiculoneuropathy (n = 4), based on the predominant neuropathic symptoms. Acute or subacute onset was seen more frequently in multiple mononeuropathy and multiple cranial neuropathy, whereas chronic progression was predominant in other forms of neuropathy. Sensory symptoms without substantial motor involvement were seen predominantly in sensory ataxic, painful sensory, trigeminal and autonomic neuropathy, although the affected sensory modalities and distribution pattern varied. In contrast, motor weakness and muscle atrophy were observed in multiple mononeuropathy, multiple cranial neuropathy and radiculoneuropathy. Autonomic symptoms were often seen in all forms of neuropathy. Abnormal pupils and orthostatic hypotension were particularly frequent in sensory ataxic, painful, trigeminal and autonomic neuropathy. Unelicited somatosensory evoked potentials and spinal cord posterior column abnormalities in MRI were observed in sensory ataxic, painful and autonomic neuropathy. Sural nerve biopsy specimens (n = 55) revealed variable degrees of axon loss. Predominantly large fibre loss was observed in sensory ataxic neuropathy, whereas predominantly small fibre loss occurred in painful sensory neuropathy. Angiitis and perivascular cell invasion were seen most frequently in multiple mononeuropathy, followed by sensory ataxic neuropathy. The autopsy findings of one patient with sensory ataxic neuropathy showed severe large sensory neuron loss paralleling to dorsal root and posterior column involvement of the spinal cord, and severe sympathetic neuron loss. Degrees of neuron loss in the dorsal and sympathetic ganglion corresponded to segmental distribution of sensory and sweating impairment. Multifocal T-cell invasion was seen in the dorsal root and sympathetic ganglion, perineurial space and vessel walls in the nerve trunks. Differential therapeutic responses for corticosteroids and IVIg were seen among the neuropathic forms. These clinicopathological observations suggest that sensory ataxic, painful and perhaps trigeminal neuropathy are related to ganglioneuronopathic process, whereas multiple mononeuropathy and multiple cranial neuropathy would be more closely associated with vasculitic process. (+info)
Motor denervation of tumors of the head and neck: changes in MR appearance.
(53/228)
PURPOSE: We reviewed the MR appearance of motor denervation of the third (mandibular) division of the trigeminal nerve (V3) and of the hypoglossal nerve. METHOD: Six cases of tumor of the head and neck with motor denervation were retrospectively evaluated. These comprised two patients with V3 denervation, three patients with hypoglossal nerve denervation, and one patient with both V3 and hypoglossal denervation. The observation was conducted for 6 to 44 months after onset. In denervated muscles, changes in signal intensity in T(1)- and T(2)-weighted images, degree of contrast enhancement, and volume of muscle were estimated during the follow-up period. RESULTS: In all cases of V3 denervation, the muscles showed no change in signal intensity in the T(1)-weighted images up to three months after onset. In two cases of hypoglossal denervation, the tongues appeared ipsilaterally hyperintense in the T(1)-weighted images within the first three months. In one case with V3 denervation and two cases with hypoglossal denervation, denervated muscles appeared hyperintense in the T(2)-weighted images up to three months after onset. At three months after denervation, the signal intensities of all motor-denervated areas increased in both T(1)- and T(2)-weighted images. Postcontrast T(1)-weighted images obtained within the first three months displayed contrast enhancement of all denervated muscles. In three cases of V3 denervation, the volumes of the affected muscles were reduced after the first three months. In three cases of hypoglossal denervation, the ipsilateral volume of the tongue decreased at three months after onset. CONCLUSION: Up to three months after onset, the denervated muscles appeared hyperintense in the T(2)-weighted images and contrast enhancement in postcontrast T(1)-weighted images before fatty infiltration and volume loss were apparent. Familiarity with the MR appearance of denervated muscles accompanying tumors of the head and neck is important to avoid confusion with inflammatory or neoplastic processes. (+info)
Clinical evidence for the onset of the sensitive period in infancy.
(54/228)
Seven neonates had a IIIrd or VIth nerve palsy or afferent visual pathway pathology at birth. These abnormalities resolved within 6 weeks and the children have developed normal visual acuity, motor fusion, and stereopsis. We conclude that there is a latent period of 6 weeks before the onset of the sensitive period. (+info)
Penetrating orbital trauma by stiletto causing complex cranial neuropathies.
(55/228)
Penetrating orbital injuries pose a serious threat to vision, ocular motility, and in some cases, life. Long, sharp stiletto objects may penetrate deeply, causing catastrophic damage to orbital structures, despite seemingly trivial entry wounds. The authors present two cases of penetrating orbital injuries by stiletto objects, both entering via small eyelid wounds. Traumatic optic neuropathy occurred in both cases, and was treated with corticosteroids, however the globes escaped direct injury. Injuries to the IIIrd and VIth cranial nerves were also observed. Deep orbital injuries must be excluded in patients presenting with small eyelid wounds caused by sharp penetrating objects. (+info)
Occipital condylar fractures. Review of the literature and case report.
(56/228)
Fractures of the occipital condyle are rare. Their prompt diagnosis is crucial since there may be associated cranial nerve palsies and cervical spinal instability. The fracture is often not visible on a plain radiograph. We report the case of a 21-year-old man who sustained an occipital condylar fracture without any associated cranial nerve palsy or further injuries. We have also reviewed the literature on this type of injury, in order to assess the incidence, the mechanism and the association with head and cervical spinal injuries as well as classification systems, options for treatment and outcome. (+info)