Cluster headache: further observations on the dissociation of pain and autonomic findings

Hemicrania continua with contralateral cranial autonomic features: a case report

BACKGROUND

Hemicrania continua is characterized by continuous strictly unilateral head pain with episodic exacerbations. Episodic exacerbations are associated with ipsilateral cranial autonomic features.

CASE DESCRIPTION

We report a 24-year female with a 2-year history of continuous right-sided headache with superimposed exacerbations. Episodic exacerbations were associated with marked agitation and contralateral cranial autonomic features. The patient showed a complete response to indomethacin within 8 hours.

DISCUSSION

The dichotomy of pain and autonomic features is in accordance with the concept about the possibility of two separate pathways for pain and autonomic features in trigeminal autonomic cephalalgias.

Disorders of the pupil

Pupil size is determined by the interaction of the parasympathetic and the sympathetic nervous system. The parasympathetic system conducts the light reaction with its major center in the dorsal midbrain. The sympathetic nervous system acts either directly on the dilator muscle (peripherally) or centrally by inhibiting the Edinger-Westphal nucleus. Psychosensory reactions are transmitted via the sympathetic system. The afferent input of the light reflex system in humans is characteristically wired, allowing a detailed analysis of a lesion of the afferent input. Even in humans a subgroup of ganglion cells containing melansopsin plays an important role as a light sensor for the pupillary system. To diagnose normal pupillary function, pupils need to be isocoric and react bilaterally equally to light. Anisocoria indicates a problem of the efferent pupillary pathway. Pupillary disorders may involve the afferent pathways (relative afferent pupillary defect) or the efferent pathways. Physiological anisocoria is a harmless condition that has to be distinguished from Horner's syndrome. In this case pharmacological testing with cocaine eye-drops is helpful. Disorders of the parasympathetic system will impair the light response. They include dorsal midbrain syndrome, third-nerve palsy, and tonic pupil. Tonic pupils are mainly idiopathic and do not need imaging. Disorders of the iris, including application of cholinergic agents, need also to be considered in impaired pupillary light reaction.