<unk>  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<unk> : * 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) that releases acetylcholine. * Third-order neuron disorder: Postganglionic lesions at the level of the internal carotid artery (e.g. a tumor in the cavernous sinus or a carotid artery dissection) that releases norepinephrine. * Partial<unk> : In case of a third-neuron disorder, anhidrosis is limited to the middle part of the forehead or can be absent, resulting in a partial<unk> . If patients have impaired sweating above the waist affecting only one side of the body, and they do not have clinically apparent<unk> , then their lesions are just below the stellate ganglion in the sympathetic chain.
Horner's syndrome
Pilotto syndrome
Nance–Horan syndrome
Erb's palsy
Brown's syndrome
Summer penile syndrome
Bell's palsy
Frey's syndrome