Central pathway of the extraocular muscle proprioception

Central projections of the ethmoidal nerve of the cat as determined by the horseradish peroxidase tracer technique

The ethmoidal nerve innervates the nasal mucosa and constitutes the afferent limb of several upper airway protective reflexes. Protective reflexes, such as sneezing, coughing, and apnea, are those reflexes that either expel foreign substances from the respiratory tract or stop them from gaining access to the lungs. The afferents for nasal receptors are thought to be a part of the trigeminal system rather than olfactory in nature. The objective of this study was to localize the cell bodies of these ethmoidal afferents and to trace the central projections of these neurons. Horseradish peroxidase was applied to the ethmoidal nerve in 11 adult cats. Following a survival period of 48-72 hours, the animals were killed and the tissue was processed according to the tetramethylbenzidine method. Reaction product was localized in cell bodies within the trigeminal ganglion, concentrated caudal to the entrance of the ophthalmic trunk of the trigeminal nerve. Transganglionic projections to the spinal trigeminal nucleus were localized primarily in the subnucleus interpolaris and in layers I and II of the subnucleus caudalis. There was also reaction product in cell bodies within the mesencephalic trigeminal nucleus. These results are in keeping with projections of other ophthalmic division receptor afferents, such as the cornea and the supraorbital nerve.

Graves' orbitopathy and the thyrotropin-releasing hormone (TRH) test

The value of the thyrotropin-releasing hormone (TRH) test may be insufficiently emphasized in the diagnosis of patients with euthyroid Graves' disease who have unexplained proptosis or vertical diplopia. We saw three patients who had these orbital symptoms and normal routine serum thyroid studies. The orbital computed tomograms (CT) found an orbital myopathy in all, and the diagnosis of Graves' orbitopathy was made by an abnormal TRH test. Not all euthyroid Graves' patients will show a positive result, but in those who do, the test is diagnostic. The clinical summaries of our three patients and the applications of the thyrotropin-releasing hormone test in ophthalmic practice are reviewed.

New observations on the representation of the eye muscle proprioception within the descending trigeminal nucleus

Units responding to stretch of single extraocular muscles were found in the bulbar and cervical portion of the descending trigeminal nucleus of the lamb. The electrolysis of these bulbar sites provoked degeneration of nervous fibres which could be followed till the first cervical segment of the spinal cord.