Abstract
Introduction
Raeder's paratrigeminal syndrome is described as unilateral head and face pain, ipsilateral oculo-sympathetic paralysis (Horner's syndrome) and ipsilateral trigeminal dysfunction or less frequently dysfunction of other cranial nerves (1). We present a rare case of Raeder's syndrome following a dissection of the petrous part of the internal carotid artery (ICA) with selective damage of Aδ fibres of the ophthalmic part of trigeminal nerve
Case report
A 38-year-old, otherwise healthy, Caucasian woman developed a severe (visual analogue scale 7–8), steady, non-throbbing pain in the right side of the head, especially in the right periorbital region. She had no history of migraine or cluster headache and no history of trauma or recent neck manipulation. Neurological examination revealed a right-sided Horner's syndrome and dissociated sensory loss of the first division of the right trigeminal nerve.
Detailed examination of cutaneous sensation revealed abolished sensation to pin prick and cold sensation, whereas the sensation to touch was only slightly diminished. Furthermore, while the electrically evoked pain threshold was increased on the right, symptomatic, side (0.8 mA/1.4 mA left vs. right side), the sensory threshold was only slightly increased (0.4 mA/0.6 mA left vs. right side). The nBR was elicited with the concentric electrode as described previously (2). Both ipsi- and contralateral responses could not be elicited when stimulated on the right, but not the left forehead. In contrast, the standard blink reflex (BR) showed normal R1 and R2 latencies and amplitudes, suggesting the selective damage of Aδ fibres. Both nBR and BR showed normal latencies and amplitudes when elicited by maxillary stimulation. Pharmacological testing of pupillary function showed absent dilatation of the right pupil to local application of cocaine and hydroxyamphetamine, confirming the postganglionic site of the oculosympathetic lesion. The sudomotor function, however, was not impaired. Magnetic resonance imaging showed a dissection of the petrous part of the ICA. The intracavernous part of the ICA was normal. Doppler/duplex sonography revealed no abnormalities. Vasculitis of the ICA caused by varicella infection, systemic vasculitis and other inflammatory diseases (such as the Tolosa–Hunt syndrome) could be excluded by cranial MRI, normal cerebrospinal fluid and clinical chemistry results or the clinical course of the disease.
Discussion
In 1918 and 1924, the Norwegian opthalmologist Georg Raeder described a syndrome of unilateral headache, facial pain and incomplete Horner's syndrome (3). Expansive pericarotid lesions such as tumours, fibromuscular dysplasia or aneurysm can lead to direct compressive injury of the trigeminal nerve (1). Also carotid artery dissection extending into the intracavernous segment raises the possibility of ‘mechanical’ involvement of trigeminal fibres. Trigeminal nerve palsy, however, has also been observed following the dissection of the extracavernous part of the ICA, probably resulting from arterio-arterial microembolization of the nutrient artery of the trigeminal nerve (4, 5).
In our case we observed a Raeder's syndrome with ipsilateral retroorbital pain, oculosympathetic palsy and alteration of the first branch of the trigeminal nerve only. The MRI revealed the dissection of the petrous part of the ICA as the underlying aetiology. The selective damage of the first trigeminal branch may be due to the microembolization of the inferiolateral trunk of the ICA, which has been shown to be the arterial supply for the third, fourth and sixth cranial nerves and the first branch of the trigeminal nerve but not for the second or third divisions (6). Moreover, we observed the dissociated sensory loss of pain and cold thermaesthesia, with an increased pain threshold, indicating the predominant damage of Aδ fibres. Using the nBR allowed electrophysiological confirmation of selective damage of trigeminal nociceptive fibres. This selective injury of the trigeminal Aδ fibres is likely to be the result of a higher susceptibility of slow conducting myelinated nerve fibres to ischaemic conditions, which has been shown in animal experiments (7).
Normal blink reflex (forehead stimulation; solid line = ipsilateral response, hairline = contralateral response) of the non-symptomatic (A) and symptomatic (B) side without significant differences in latencies and amplitudes. Nociceptive blink reflex (forehead stimulation; solid line = ipsilateral response, hairline = contralateral response) of the non-symptomatic (C) side with a normal R2 response and the symptomatic (D) side with a complete loss of ipsilateral and contralateral response. Nociceptive blink reflex (maxillary stimulation; solid line = ipsilateral response, hairline = contralateral response) of the non-symptomatic (E) and symptomatic (F) side without significant differences in latencies and amplitudes.
In summary, we present a rare case of Raeder's syndrome following spontaneous dissection of the petrous part of the ICA with the uncommon dissociated sensory loss due to selective impairment of Aδ fibres in the first division of the trigeminal nerve. The nociceptive blink reflex revealed changes in the trigeminal nociception that would not have been detected by normal BR recordings and may be a useful tool in clinical practice.