Psychometric functions for efficient and effective psychophysical testing of sensory function.

An efficient test for sensory function has been reported using random order pairs of real and sham stimuli. The constant magnitude of the real stimulus is chosen such that the first error in a patient's forced-choice report on the order of real and sham stimulation, immediately indicates abnormal sensory function. This magnitude just exceeds a critical large percentile of the psychometric function (i.e. the relationship between percentage of detection and stimulus magnitude in healthy subjects). The aim was to determine psychometric functions for one tongue site and six facial sites for adjusting three variants of the real/sham stimulus method (i.e. for light touch, cold sensation and for two-point discrimination). All 150 healthy subjects participated in testing for light touch sensation, 100 subjects additionally participated in testing two-point discrimination and 50 subjects participated additionally in testing cold sensation. The stimulus magnitude was varied using a staircase-limits procedure. Following curve fitting with a Boltzmann function, 90th, 95th or 99th percentiles of the psychometric functions were determined. A set of at least two real/sham tests, one testing the function of large nerve fibres and one for small fibres, allows quick assessment of a patient's disturbed sensory function including its fibre pathology.

Extension of normal values on sensory function for facial areas using clinical tests on touch and two-point discrimination.

The threshold value of a sensory test provides a numerical measure of the sensory function. In order to decide whether a threshold value from an affected site indicates 'abnormal' sensory function, it can be compared with normal values from a healthy control population. The aim of this study was to extend current information on normal values for static light touch and static two-point discrimination for facial sites. Using simple hand-held devices, 95% upper limits of confidence intervals of threshold values were determined for facial sites other than those studied previously and for a large sample of 100 healthy subjects. The MacKinnon-Dellon Disk-Criminator and the Aesthesiometer were used to measure novel normal values of two-point discrimination. As threshold values for two-point discrimination from the Aesthesiometer were similar to those obtained using the Disk-Criminator, the use of the Aesthesiometer might not be indicated. Apart from the Pressure Specified Sensory Device (a device with pressure control), Semmes-Weinstein nylon monofilaments and the Disk-Criminator are useful devices for studying sensory function, in particular under clinical test conditions in which easy and fast application are advantageous.

Testing of iatrogenic lingual nerve injury using a novel psychophysical method and oral reflexes.

In a case of long-term sensory loss in the tongue following third molar extraction, a novel, efficient and effective psychophysical test was used. This initial test, which includes the presentation of pairs of a real and fake stimulus, and a forced-choice response, was applied to determine whether relatively thick or thin afferent fibres of the lingual nerve were affected. The results suggested that thick fibres on the right tongue side were mainly affected. Sensory loss was confirmed and its extent assessed by a standard test determining thresholds of light touch. Furthermore, sensory function was determined by an objective test based on inhibitory reflexes in masseteric electromyographic activity following electrical stimulation of oral tissue. Reflex features that are important for within-patient diagnosis are a difference between the injured and control sides in latency of the first reflex, and also in depth-contrast in signal amplitude between both sides at the post-stimulus time of the trough of an inhibition on the uninjured side. In agreement with the findings from the psychophysical tests, the finding of the absence of an early component of both inhibitions suggested sensory loss related to dysfunction of fast-conducting, relatively thick afferent fibres of the lingual nerve. Apart from being used for medicolegal reasons, the objective reflex test may have conclusive prognostic value or may influence surgical therapeutic decisions.

[Repair and revision 9. Peripheral trigeminal nerve injury]. / Reparatie en revisie 9. Perifeer trigeminaal zenuwletsel.

A review is given about long-term incidence of sensory disturbance in the areas of innervation of the n. trigeminus for different types of trauma and/or treatment. Diagnosis, clinical course and possible types of treatment are in addition reviewed. Regarding diagnosis, the outcome of a test on sensory function is not always related to the degree of nerve damage because methods differ in the type of afferent nerve fibers of which function is tested, and some specificity might occur in nerve damage, i.e. either thick or thin afferent fibers might be predominantly affected at a particular time. An initial quick testing of sensory function is recommended. This testing includes examining two sensory modalities, which are related to functioning of thick and thin afferent fibers respectively and which have a dichotomous yes/no outcome on the incidence of a pronounced sensory disturbance.

Information on infraorbital nerve damage from multitesting of sensory function.

Sensory disturbance following orbitozygomatic complex fractures was studied in 65 patients from 4 treatment groups which represented potentially varying degrees of sensory disturbance. The fracture-type-dependent treatments were: no surgical intervention (n = 20), closed reduction with or without wire fixation (n = 17), open reduction with miniplate fixation (n = 15) and/or reconstruction of the orbital floor (n = 13). In order to assess the sensory function of different classes of afferent fibres, several methods of sensory testing were applied. On average 6.3 months after treatment, the patient's report was obtained, and tests regarding touch, two methods of two-point discrimination, and cold were applied on the cheek and upper lip. The degree of sensory disturbance was method-dependent. In patients who underwent closed reduction, pronounced levels of positive correlation occurred between results from different tests or from both test sites. The levels of these correlations were, in general, low for all other treatments. These findings suggest that afferent fibres of both large and small diameter tended to be permanently damaged in the patient group with closed reduction. In contrast, the types of sensory afferent fibres that were involved in the trauma and/or their recovery were highly variable within patients and sites for all other treatment groups.

Infraorbital nerve function following treatment of orbitozygomatic complex fractures. A multitest approach.

Sensory disturbance following orbitozygomatic complex fractures was studied in 65 patients in relation to type of fracture and method of treatment. The fracture-type-dependent treatments were: no surgical intervention (n = 20), closed reduction with or without wire fixation (n = 17), open reduction with miniplate fixation (n = 15) and/or reconstruction of the orbital floor (n = 13). Several methods were applied to assess sensory function, on average 6.3 months after treatment, i.e. the patient's report and tests regarding touch, two methods of two-point discrimination, and cold, all applied on the cheek and upper lip. The various examinations indicated that, on average, the long-term sensory disturbance was most pronounced and severe in patients who underwent closed reduction without miniplate fixation. As the sensory disturbance of patients with open reduction and miniplate fixation approached the base-line level of patients for whom surgical intervention was not indicated, open reduction with miniplate fixation can be recommended as treatment for frontozygomatic suture fractures. The degree of sensory disturbance of patients who underwent orbital floor reconstruction was intermediate compared to patients with closed and open reduction respectively.

[Simple assessment of trigeminal nerve injury]. / Eenvoudig onderzoek naar letsel van de nervus trigeminus.

This paper describes a simple method to assess trigeminal nerve injury. An easy and feasible technique, in particular for the dental surgeon, is scanning the area with altered sensation as indicated by the patient. It is important to refer the eligible patient in time for microsurgical repair of the damaged nerve.

Recovery of sensation in the radial forearm free flap in oral reconstruction.

The purpose of this study was to find out to what extent sensory function recovers in a free radial forearm flap used for intraoral reconstruction after surgery for oral cancer. In 40 free radial forearm flaps we investigated the perception of light touch, two-point discrimination, pain, directional sensation, and temperature between 6 months and 11 years after flap transfer to the oral cavity. Four flaps (10 percent) were anesthetic, 21 flaps (52.5 percent) recovered partly, and 15 flaps (37.5 percent) had perception of all sensory modalities tested in at least two-thirds of the flap area. All patients with positive sensation in the surrounding area subsequently had good sensory recovery in the flap. This suggests that recovery of sensation in a nonreinnervated free flap is due to nerve ingrowth from the surrounding mucosa. The present results suggest that sensory function in intraoral free radial forearm flaps returns again. Further study is necessary to define the use of neurofasciocutaneous radial forearm flaps in reconstruction of the oral cavity.

Morbidity of the infraorbital nerve following orbitozygomatic complex fractures.

Acute sensory disturbances in the distribution of the infraorbital nerve are recognised signs present in patients with orbitozygomatic complex fractures. Fifty consecutive patients with unilateral orbitozygomatic complex fractures were evaluated with regard to the long-term infraorbital nerve sensory function. The highest incidence of long-term neurosensory deficits occurred in fractures with an undistracted frontozygomatic suture. This is in complete agreement with the distribution of long-term neurosensory deficits regarding the method of treatment for orbitozygomatic complex fractures. In our series slightly more than one-third of the patients had third or fourth degree nerve injuries, according to Sunderland's classification, to the infraorbital nerve following orbitozygomatic complex fractures. This outcome should influence the management of orbitozygomatic complex fractures. With regard to fixation of unstable malar fractures in relation to sensory recovery of the infraorbital nerve, miniplate osteosynthesis is recommended as opposed to wire fixation in all unstable bone fractures when there is displacement. Furthermore, open reduction and fixation of an orbitozygomatic complex fracture offer a better prognosis for complete recovery of the infraorbital nerve function than elevation only with or without Kirschner wire fixation.

A reappraisal of the platysma myocutaneous island flap. A follow-up study of the functional outcome after reconstruction of the floor of the mouth.

The functional results of primary reconstruction of the floor of the mouth after ablative surgery for oral cancer using a platysma myocutaneous island flap are reviewed. Seventeen patients who had simultaneous neck dissection, tumor resection, and reconstruction were evaluated. It appears from this study that primary reconstruction of the floor of the mouth with a platysma flap is not ideal. This is believed to be due partly to the high occurrence of direct, postoperative complications.

Magnetic resonance assessment of microvascular patency in reimplanted rabbit ears.

RATIONALE AND OBJECTIVES: Magnetic resonance angiography (MRA) provides a means of noninvasive vascular imaging of microvascular vessels. Before conducting comparative studies and value assessments of a new method, it is necessary to evaluate the reproducibility and reliability of the technique. In an experimental study with five rabbits, we investigated the feasibility of MRA imaging of microsurgical vessels. We also attempted to demonstrate the reproducibility of the method. METHODS: We performed MRA imaging of the vascular tree of five New Zealand white rabbit ears, including normal ears, after microvascular reimplantation of the ear and in occlusion experiments on the ear. Scans of four reimplanted ears were performed after the microvascular procedure. In four occlusion experiments, the central vessels were totally occluded by a ligature, and scans were carried out prior to and immediately after occlusion. We used a fast imaging with steady-state precession (FISP) three-dimensional (3-D) rephased-dephased sequence (28-msec repetition time [TR], 18-msec echo time [TE], and a 20 degrees flip angle). RESULTS: In normal rabbit ears and in the reimplantation cases, MRA imaging was able to show the flow within the vascular tree. In the reimplanted ears, MRA images confirmed patency in all anastomosed vessels. The diagnosis of occlusion appeared to be secure in the fully completed experiments (two of four) when it was based on the absence of a signal in the occluded vessels. Because of poor image quality during preligation scanning, we prematurely canceled two experiments. CONCLUSIONS: This study demonstrates that MRA imaging could correctly identify 1-mm vascular channels. Because of the long acquisition time, motion could compromise the reliability of the technique in human subjects.

Autogenous transplantation of third molars in irradiated jaws--a preliminary report.

Our experience with third molar autotransplants in 2 patients, into an area irradiated at an early age, is described and discussed. It is shown that such autotransplantations are possible.

Assessment of trigeminal nerve function by means of short-latency somatosensory evoked potentials after microneurosurgical repair.

In order to evaluate accurately trigeminal nerve damage and the response to microneurosurgical treatment, a reproducible, objective test of trigeminal nerve function is required. This study investigates the use of somatosensory evoked potentials as an objective monitor of trigeminal nerve function after microneurosurgical repair. We examined 10 patients, all but 1 treated for gnathic disorders, in whom a severe iatrogenic injury to the inferior alveolar nerve occurred unilaterally. One patient underwent partial mandibulectomy with sacrifice of the nerve because of a malignant tumour. A significant difference in trigeminal somatosensory evoked potential latencies after stimulation of the normal side of the lower jaw compared with the response after stimulation of the affected side was to be expected. Immediate microneurosurgical repair was carried out in 7 patients. The trigeminal somatosensory evoked potential latencies after right and left sided stimulation of the mandible did not differ significantly after subjective successful microneurosurgical repair. Somatosensory evoked potential testing appears to represent an objective method of evaluating trigeminal nerve function, in particular in relation to microneurosurgical procedures. The results of trigeminal testing should improve after technical refinement.