A longitudinal study of multimodal evoked potentials in patients following radiotherapy for nasopharyngeal carcinoma

Motor cortex evaluation by nTMS after surgery of central region tumors: a feasibility study

BACKGROUND

Largely discussed during the past decade, motor cortex reorganization in brain tumor surgery has been investigated only by few studies. We therefore aimed to investigate cortical motor representation after resection of perirolandic WHO grade II and III gliomas using navigated transcranial magnetic stimulation (nTMS).

METHODS

Five patients were examined before neurosurgery and after a follow-up period of 17.7 ± 6.8 months. As a control, five healthy age-matched subjects were equally studied by nTMS in two sessions spaced 12.6 (range 2-35) days apart. Resting motor thresholds (RMT), hotspots and centers of gravity (CoG) were identified for the first dorsal interosseous (FDI), abductor pollicis brevis (APB), extensor digitorum (EXT), tibialis anterior (TA) and abductor hallucis (AH) muscles. Euclidian distances, coefficients of variance and intraclass correlation coefficients (ICC) were calculated.

RESULTS

Healthy subjects showed moderate to excellent reliability measurement of RMT (ICC = 0.69-0.94). Average displacement of CoGs across sessions was 0.68 ± 0.34 cm in the dominant and 0.76 ± 0.38 cm in the non-dominant hemisphere; hotspots moved 0.87 ± 0.51 cm and 0.83 ± 0.45 cm, respectively. In one patient these parameters differed significantly from the control group (p < 0.05 for both CoGs and hotspots). Overall, all patients' CoGs moved 1.12 ± 0.93 cm, and hotspots were 1.06 ± 0.7 cm apart. In both patients and healthy subjects, movement of assessed parameters was more important along the X- than the Y-axis.

CONCLUSIONS

nTMS allows evaluating cortical reorganization after brain tumor surgery. It may contribute to the understanding of neurofunctional dynamics, thus influencing therapeutic strategy.

Effects of radiotherapy on olfactory function

BACKGROUND AND PURPOSE

Changes in olfactory function have been reported in patients receiving significant doses of radiation to the olfactory epithelium. Aim of this study was to investigate severity and time course of changes in olfactory function in patients irradiated for tumours of the head and neck region.

MATERIAL AND METHODS

Forty-four patients receiving radiotherapy (RT) for tumours in the area of the head and neck participated (16 women, 28 men; age 11-81 y; mean 55 y). Olfactory function was measured before and bi-weekly during RT for 6 weeks. A subgroup (25 patients) was followed for 12 months. Patients were divided into two groups according to the dose to the olfactory epithelium. Twenty-two patients ('OLF group') had radiation doses to the olfactory epithelium between 23.7 and 79.5 Gy (median 62.2 Gy). In the 22 patients of the 'non-OLF group' the dose applied to the olfactory epithelium was significantly lower (2.9-11.1 Gy, median 5.9 Gy). Total tumour dose (30-76.8 Gy), age, sex distribution, and baseline chemosensory function were not significantly different between groups. Testing was performed for odour identification, odour discrimination, and olfactory thresholds.

RESULTS

Odour discrimination, but not odour identification or odour threshold, was significantly decreased 2-6 weeks after begin of therapy in the OLF group. In addition, a significant effect of the radiation dose was observed for odour discrimination. More than 6 months after therapy, OLF group patients had significantly lower odour identification scores compared to the non-OLF group.

CONCLUSION

As indicated through the non-significant change of olfactory thresholds, the olfactory epithelium is relatively resistant against effects of radiation. It is hypothesized that RT has additional effects on the olfactory bulb/orbitofrontal cortex responsible for the observed changes of suprathreshold olfactory function.

Lhermitte's sign among nasopharyngeal cancer patients after radiotherapy

BACKGROUND

Lhermitte's sign (LS) is a side effect of radiotherapy (RT) on the spinal cord and typically occurs shortly after the procedure has been conducted. When treating patients with cancer of the head and neck region with irradiation, it remains difficult to avoid exposing the cervical spinal cord to unintended radiation. In this study, we focused on nasopharyngeal cancer (NPC) alone and looked for various parameters that might influence the occurrence of LS associated with this disease after RT.

METHODS

From 1979 through 1990, 1171 patients with NPC completed RT either with or without chemotherapy at the Lin-Kou Medical Center, Chang Gung Memorial Hospital (CGMH), Tao-Yuan, Taiwan; the RT regimens for these treated patients were very similar. The nasopharyngeal tumor was treated to 75 Gy by photon teletherapy and after-loading brachytherapy. The neck lymphatics were irradiated with photon irradiation to 46.8 Gy and then boosted with electron beams to 10 to 30 Gy, in accordance with the patient's nodal status, either unilaterally or bilaterally. Every patient was followed monthly for the first 3 months after therapy and subsequently every 2 to 3 months for the next 2 years and, finally, every 6 months thereafter. At follow-up, a neurologic checkup of each patient was performed to determine whether any injury to the spinal cord or brain stem had arisen.

RESULTS

LS was observed for 121 patients (10.3%). The median development time for such signs was 3.0 months after the completion of RT (range, 0.2-72 months), and the appearance of such a sign lasted 1 to 82 weeks (median, 17 weeks). No statistically significant differences between the sexes were noted in the development of such a sign (p = .5263),or among various T classifications (p = .0757) and N classifications (p = .4412). The incidence of LS was significantly lower for those patients who had also received chemotherapy than it was for those who had not (p = .003), and it was also lower for patients older than 60 years than for those younger than 60 years (p = .0061). Of the subjects who did not undergo neck-lymphatic boosting or who had undergone only unilateral neck-lymphatic boosting, 7.2% had LS develop, whereas 11.5% of patients who had been boosted bilaterally had LS develop (p = .0285).

CONCLUSIONS

The incidence of LS associated with NPC and after RT was higher in patients who underwent bilateral neck-lymphatic boosting by electron beams than for those who underwent unilateral boosting or who did not undergo boosting. A correlation between increased incidence of LS and RT dose on the cervical spinal cord was noted when the cord dose exceeded 48.9 Gy. Therefore, wherever possible, a CT simulator and a three-dimensional treatment-planning system should necessarily be used to verify the dose distribution of electron-beam RT to diminish the chance of radiation overdose on the cervical cord.

Olfactory function in patients with nasopharyngeal carcinoma following radiotherapy

The aim of this study was to examine the impact of radiation treatment on olfactory function in patients with nasopharyngeal carcinoma (NPC). An olfactory function test battery was administered to 25 adult NPC patients having received radiotherapy, 24 adult nasopharyngeal carcinoma patients awaiting to receive radiation treatment, and 36 adult normal control subjects. Members of the three groups were matched in terms of age, educational level, and full-scaled IQ score. Comparing the test results revealed that the NPC patients with radiotherapy had olfactory information processing impairments including absolute threshold, odour-tactile cross-modality matching, verbal identification of odours, and recall and recognition of identity of odours. The deficits of suprathreshold olfactory functioning in these patients did not seem to arise from impaired absolute threshold sensitivity. Provided that the results are reproducible, an evaluation of olfactory functioning in NPC patients during the period of radiotherapy may be useful for detecting or even avoiding side effects of radiation.