BackgroundThe periaqueductal gray region (PAG) is one of several brain areas identified to be vulnerable to structural and functional change following peripheral nerve injury. Sciatic nerve constriction injury (CCI) triggers neuropathic pain and three distinct profiles of changes in complex behaviours, which include altered social and sleep–wake behaviours as well as changes in endocrine function. The PAG encompasses subgroups of the A10 dopaminergic and A6 noradrenergic cell groups; the origins of significant ascending projections to hypothalamic and forebrain regions, which regulate sleep, complex behaviours and endocrine function. We used RT-PCR, western blots and immunohistochemistry for tyrosine hydroxylase to determine whether (1) tyrosine hydroxylase increased in the A10/A6 cells and/or; (2) de novo synthesis of tyrosine hydroxylase, in a ‘TH-naïve’ population of ventral PAG neurons characterized rats with distinct patterns of behavioural and endocrine change co-morbid with CCI evoked-pain.ResultsEvidence for increased tyrosine hydroxylase transcription and translation in the constitutive A10/A6 cells was found in the midbrain of rats that showed an initial 2–3 day post-CCI, behavioural and endocrine change, which recovered by days 5–6 post-CCI. Furthermore these rats showed significant increases in the density of TH-IR fibres in the vPAG.ConclusionsOur data provide evidence for: (1) potential increases in dopamine and noradrenaline synthesis in vPAG cells; and (2) increased catecholaminergic drive on vPAG neurons in rats in which transient changes in social behavior are seen following CCI. The data suggests a role for dopaminergic and noradrenergic outputs, and catecholaminergic inputs of the vPAG in the expression of one of the profiles of behavioural and endocrine change triggered by nerve injury.

Bone sarcoidosis is an uncommon manifestation of the multisystemic disease with skull involvement being rare. We present the case of a 32-year-old female who was referred by her General Practitioner with a left calvarial lesion on a background of previous unilateral 7th nerve palsy and diabetes mellitus. Images demonstrated a left frontoparietal calvarial osteolytic lesion. She underwent resection by the neurosurgical team with histopathological study revealing noncaseating granulomas, consistent with sarcoidosis. Given absence of other systemic features of sarcoidosis, she did not undergo systemic treatment.

Post-aural pain is a non-specific symptom, and, with normal clinical and audiometric test results, rare lesions such as the one presented could be easily missed. A thorough clinical examination must be performed to identify genuine signs, and appropriate imaging undertaken to exclude rare causes, such as this metastatic lesion of the temporal bone.