Ans. B: Proptosis When all the sympathetic function on one side is lost, resulting in miosis, a narrowed palpebral fissure and slight enophthalmos (due to loss of tone of Muller muscle), sometimes associated with unilateral absence of sweating, the condition is called the Homer syndrome Homer's syndrome/ Bernard-Homer syndrome/ Claude Bernard-Homer syndrome/ Oculosympathetic palsy It is the combination of drooping of the eyelid (ptosis) and constriction of the pupil (miosis), sometimes accompanied by decreased sweating of the face on the same side. It indicates a problem with the sympathetic nervous system. Signs and symptoms Signs that are found in all patients on the affected side of the face include paial ptosis (drooping of the upper eyelid from loss of sympathetic innervation to the superior tarsal muscle, also known as Muller's muscle); upside-down ptosis (slight elevation of the lower lid); anhidrosis (decreased sweating on the affected side of the face); miosis (small pupils); enophthalmos (the impression that the eye is sunk in); loss of ciliospinal reflex; and bloodshot conjunctiva, depending on the site of lesion. Sometimes there is flushing on the affected side of the face due to dilation of blood vessels under the skin. The pupil's light reflex is maintained as this is controlled the parasympathetic nervous system. In children, Homer's syndrome sometimes leads to heterochromia: a difference in eye color between the two eyes. This happens because a lack of sympathetic stimulation in childhood interferes with melanin pigmentation of the melanocytes in the superficial stroma of the iris. Causes Homer syndrome is acquired as a result of disease but may also be congenital (inborn) or iatrogenic. Although most causes are relatively benign, Homer syndrome may reflect serious disease in the neck or chest (such as a Pancoast tumor (tumor in the apex of the lung) or thyrocervical venous dilatation). Due to lesion or compression of one side of the cervical or thoracic sympathetic chain, which generates symptoms on the ipsilateral side of the body. Lateral medullary syndrome Cluster headache - combination termed Hoon's headache Trauma- base of neck, usually blunt trauma, sometimes surgery. Tumours - often bronchogenic carcinoma of the superior fissure (Pancoast tumor) on apex of lung Aoic aneurysm, thoracic Cervical rib traction on stellate ganglion Cavernous sinus thrombosis Sympathectomy Nerve blocks, such as cervical plexus block, stellate ganglion or interscalene block Pathophysio logy Homer syndrome is due to a deficiency of sympathetic activity. The site of lesion to the sympathetic outflow is on the ipsilateral side of the symptoms. The following are examples of conditions that cause the clinical appearance of Homer's syndrome: First-order neuron disorder: Central lesions that involve the hypothalamospinal tract (e.g. transection of the cervical spinal cord). Second-order neuron disorder: Preganglionic lesions (e.g. compression of the sympathetic chain by a lung tumor). Third-order neuron disorder: Postganglionic lesions at the level of the internal carotid aery (e.g. a tumor in the cavernous sinus or a carotid aery dissection). Paial Homer's syndrome In case of a third-neuron disorder, anhidrosis is limited to the middle pa of the forehead or can be absent, resulting in a paial Homer's syndrome. If someone has impaired sweating above the waist affecting only one side of the body, yet they do not have a clinically apparent Homer's syndrome, then the lesion is just below the stellate ganglion in the sympathetic chain. Diagnosis Three tests are useful in confirming the presence and severity of Homer syndrome: 1. Cocaine drop test: Cocaine eyedrops block the reuptake of norepinephrine resulting in the dilation of a normal pupil. However, in Homer's syndrome the lack of norepinephrine in the synaptic cleft causes mydriatic failure. A more recently introduced approach that is more dependable and obtes the difficulties in obtaining cocaine is to apply the alpha-agonist apraclonidine to both eyes and observe the reversal of miosis on the affected side of Homer syndrome (the opposite effect to what the cocaine test would produce in the presence of Horner's). 2. Paredrine test: This test helps to localize the cause of the miosis. If the third order neuron (the last of three neurons in the pathway which ultimately discharges norepinephrine into the synaptic cleft) is intact, then the amphetamine causes neurotransmitter vesicle release, thus releasing norepinephrine into the synaptic cleft and resulting in robust mydriasis of the affected pupil. If the lesion itself is of the third order neuron, then the amphetamine will have no effect and the pupil remains constricted. There is no pharmacological test to differentiate between a first and second order neuron lesion. 3. Dilation lag test It is impoant to distinguish the ptosis caused by Homer's syndrome from the ptosis caused by a lesion to the oculomotor nerve. In the former, the ptosis occurs with a constricted pupil (due to a loss of sympathetics to the eye), whereas in the latter, the ptosis occurs with a dilated pupil (due to a loss of innervation to the sphincter pupillae). In a clinical setting, these two ptoses are fairly easy to distinguish. In addition to the blown pupil in a CNIII (oculomotor nerve) lesion, this ptosis is much more severe, occasionally occluding the whole eye. The ptosis of Homer syndrome can be quite mild or barely noticeable (paial ptosis). When anisocoria occurs and the examiner is unsure whether the abnormal pupil is the constricted or dilated one, if a one-sided ptosis is present then the abnormally sized pupil can be presumed to be on the side of the ptosis.