Abstract
Parotid gland tumor surgery sometimes leads to facial nerve paralysis. Malignant more than benign tumors determine nerve function preoperatively, while postoperative observations based on clinical, histological and neurophysiological studies have not been reported in detail. The aims of this pilot study were evaluation and correlations of histological properties of tumor (its size and location) and clinical and neurophysiological assessment of facial nerve function pre- and post-operatively (1 and 6 months). Comparative studies included 17 patients with benign (n = 13) and malignant (n = 4) tumors. Clinical assessment was based on House–Brackmann scale (H–B), neurophysiological diagnostics included facial electroneurography [ENG, compound muscle action potential (CMAP)], mimetic muscle electromyography (EMG) and blink-reflex examinations (BR). Mainly grade I of H–B was recorded both pre- (n = 13) and post-operatively (n = 12) in patients with small (1.5–2.4 cm) benign tumors located in superficial lobes. Patients with medium size (2.5–3.4 cm) malignant tumors in both lobes were scored at grade I (n = 2) and III (n = 2) pre- and mainly VI (n = 4) post-operatively. CMAP amplitudes after stimulation of mandibular marginal branch were reduced at about 25 % in patients with benign tumors after surgery. In the cases of malignant tumors CMAPs were not recorded following stimulation of any branch. A similar trend was found for BR results. H–B and ENG results revealed positive correlations between the type of tumor and surgery with facial nerve function. Neurophysiological studies detected clinically silent facial nerve neuropathy of mandibular marginal branch in postoperative period. Needle EMG, ENG and BR examinations allow for the evaluation of face muscles reinnervation and facial nerve regeneration.
Highlights
One of the most crucial complications which accompanies parotid gland tumor surgery is the high risk of facial nerve paralysis
In the majority of the patients with benign tumors the House–Brackmann scale (H–B) scores were I at all three observation periods
The compound muscle action potential (CMAP) amplitude parameter recorded from orbicularis oris muscle (Fig. 3A, b) significantly decreased at second observation period in patients with benign tumors
Summary
One of the most crucial complications which accompanies parotid gland tumor surgery is the high risk of facial nerve paralysis. Earlier clinical studies [1, 2] and recent research projects of Lim et al [3] and Barzan et al [4] indicated the relationship between the type of surgery (surgical technique and its range which is related to tumor type and its location) and different degree of iatrogenic nerve injury. Malignant or benign type of parotid gland tumors is determined by the fine needle aspiration biopsy (FNA), intraoperative evaluation and postoperative histopathological examinations. In clinical examination proper function of the facial nerve before surgery cannot exclude its subclinical dysfunction. Electroneurographic studies showed that slowly growing tumors may not evoke the clinical symptoms of the facial
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