Little is known about the effects of undernutrition on the specific muscles and neuronal circuits involved in mastication. The aim of this study was to document the effects of neonatal low-protein diet on masticatory efficiency. Newborn rats whose mothers were fed 17 % (nourished (N), n 60) or 8 % (undernourished (U), n 56) protein were compared. Their weight was monitored and their masticatory jaw movements were video-recorded. Whole-cell patch-clamp recordings were performed in brainstem slice preparations to investigate the intrinsic membrane properties and N-methyl-d-aspartate-induced bursting characteristics of the rhythmogenic neurons (N, n 43; U, n 39) within the trigeminal main sensory nucleus (NVsnpr). Morphometric analysis (N, n 4; U, n 5) were conducted on masseteric muscles serial cross-sections. Our results showed that undernourished animals had lower numbers of masticatory sequences (P=0·049) and cycles (P=0·045) and slower chewing frequencies (P=0·004) (N, n 32; U, n 28). Undernutrition reduced body weight but had little effect on many basic NVsnpr neuronal electrophysiological parameters. It did, however, affect sag potentials (P<0·001) and rebound firing (P=0·005) that influence firing pattern. Undernutrition delayed the appearance of bursting and reduced the propensity to burst (P=0·002), as well as the bursting frequency (P=0·032). Undernourished animals showed increased and reduced proportions of fibre type IIA (P<0·0001) and IIB (P<0·0001), respectively. In addition, their fibre areas (IIA, P<0·001; IIB, P<0·001) and perimeters (IIA, P<0·001; IIB, P<0·001) were smaller. The changes observed at the behavioural, neuronal and muscular levels suggest that undernutrition reduces chewing efficiency by slowing, weakening and delaying maturation of the masticatory muscles and the associated neuronal circuitry.

This case report presents two very unusual cases of melanomas arising within the masseter muscle. Both were metastases of unknown origin arising in young, healthy patients and presenting as asymptomatic lesions. No primary lesions were found in either case. A comprehensive search of the world literature revealed no previous similar cases.

In this case report, we present a solitary metastasis of renal cell carcinoma inside the masseter muscle. To our knowledge, it is the very first case ever encountered.

The masseteric space is an important tissue compartment of the neck, but disease in it is difficult to diagnose and treat. In this paper a case of a young adult male with an abscess of the submasseteric space is presented. Diagnosis was established by computed tomography (CT) of the neck, but the severity of the lesion was not accurately estimated. Surgical intervention was performed and a large quantity of pus was drained. A detailed medical history and clinical examination of the patient as well as CT are important tools in the accurate diagnosis and efficient treatment of the disease.

This case highlights a potentially disabling complication of intermittent claudication inthe region of the masseter muscles on mastication, following bilateral external carotid artery ligation for epistaxis. Although there have been few reports of this complication this may be a reflection of the fact that the operation is rarely performed, and not because the complication is rare. Its potentially disabling nature, and its possible common occurrence after this procedure make awareness of it by surgeons who may carry out this procedure important.

Masseter muscle enlargement is one of the differential diagnoses of swelling of the cheek. We discuss a uniquecase of a malignant tumour of the masseter which was found to be a peripheral primitive neuroectodermaltumour (PNET). A review of tumours of the masseter is presented.

Both primary and metastatic malignancies of the masseter muscle are rare. We report a case of metastatic renal cell carcinoma to the masseter muscle. It was incidentally found as a hypervascular mass in carotid angiography for delineating a recurrent metastatic brain tumour. Prior to surgical removal, intravascular embolization via the left facial artery was performed in order to decrease intra-operative bleeding. The tumour was removed with minimum damage to the muscle fibres by the extraoral method, followed by a transient lower lip palsy. Metastatic intramuscular tumours, which are assumed to be due to haematogenous spread, are generally a sign of poor prognosis.