| Summary: | This thesis examines and compares the demographics, clinical phenotype, radiological findings and response to medical and surgical treatments of SUNCT (short-lasting unilateral neuralgiform headache attacks with conjunctival injection and tearing) and SUNA (short-lasting unilateral neuralgiform headache attacks with autonomic symptoms). Given the similarities between SUNCT, SUNA and trigeminal neuralgia (TN), the demographics and clinical phenotype of these disorders were also compared. In the first study (Chapter 2) a cohort of 133 patients (SUNA=63 and SUNCT=70) was phenotyped and the clinical characteristics of SUNA compared to those of SUNCT. Statistically significant predictors for SUNCT rather than SUNA were only found for ipsilateral ptosis [OR: 3.37 (95% CI: 1.50, 7.66), p < 0.0001] and rhinorrhoea [OR: 2.42 (95% CI: 1.09, 5.41), p=0.034]. Furthermore, a significantly higher proportion of SUNCT patients (n=56, 80.0%) reported marked lacrimation compared to SUNA patients (n=20, 46.5%) (P < 0.001). In the second study (Chapter 3) 45 SUNCT and 34 SUNA patients had high-resolution cisternal imaging MRI scans to asses the presence of trigeminal neurovascular conflict. The prevalence of neurovascular contact on the symptomatic trigeminal nerves was higher (57.3%) than on the asymptomatic trigeminal nerves (25%) (P≤0.001). Severe neurovascular contacts were considerably more prevalent on the symptomatic side (47.6%), compared to the asymptomatic side (11.8%) (P≤0.001). There was no statistically significant difference in the proportion of neurovascular contacts on the symptomatic nerves between SUNCT (61.7%) and SUNA (57.1%) (P=0.67). The presence of a vascular contact and its location at the root entry zone were strong predictors for the nerve to be symptomatic rather than asymptomatic. In the third study (Chapter 4) the response to treatments of 161 SUNCT and SUNA patients was analysed. Our findings suggest that lamotrigine was the most effective treatment (responders: SUNCT= 53.5%, SUNA= 57.9%) followed by oxcarbazepine (responders: SUNCT= 44.8%, SUNA= 47.0%); duloxetine and topiramate were more effective in SUNCT rather than SUNA (duloxetine responders: SUNCT= 45.0%, SUNA: 11.8%; p= 0.027; topiramate responders: SUNCT= 33.3%, SUNA= 10.7%; p=0.028). Amongst transitional treatments intravenous lidocaine led to a significant headache improvement in 83.3% SUNCT (n=25) and in 76.5% SUNA (n=13) patients (p=0.73). A greater occipital nerve block was beneficial in 27.3% (n=21) of patients for a median of 21 days (IQR: 53 days; range: 1 to 150 days), without any significant difference between SUNCT (24.4%; n=11) and SUNA (37.0%; n=10) patients (p=0.42). We found intravenous dihidroergotamine able to worsen or even to precipitate a de novo SUNCT/SUNA when administered to manage a different primary headache disorder. In the fourth study (Chapter 5) occipital nerve stimulation (ONS) was tried in nine and trigeminal microvascular decompression was tried in ten refractory, chronic SUNCT and SUNA patients. At a median follow-up of 38 months (range 24-55 months) ONS led to a marked headache improvement in eight of the nine patients (89%). One patient did not report any benefit from the stimulator at 24 months’ follow-up and opted to have the ONS explanted. At a mean follow-up fo 19.6 months (range: 12-36 months) after trigeminal microvascular decompression surgery, seven patients (70%) became headache-free after the operation. Five of the seven patients (71.4%) remained headache-free at the last follow-up. The remaining two patients were headache-free respectively for 9 and 12 months before the headache relapsed. There were no major surgical and post-surgical complications. A comparison of the clinical phenotype of SUNA (n=133) and TN (n=79) was undertaken in the last study (Chapter 6). Several similarities between SUNA and TN were found. Furthermore, some clinical features, namely pain location in V1 (OR: 11.29 95%CI: 3.92, 35.50, p < 0.001), spontaneous only attacks (OR: 44.40, 95%CI: 4.50, 437.83, p=0.001) and a chronic pain pattern (OR: 13.19, 95%CI: 4.04, 43.08, p < 0.001) predicted the diagnosis of SUNA rather than TN. Similarly duration of the attacks < 1 minute (OR: 7.95, 95%CI: 2.30, 27.57, p=0.001) and the presence of a refractory period in between triggered attacks (OR: 0.06; 95%CI: 0.02, 0.28, p-value < 0.001) were predictors for TN rather than SUNA. In summary our novel findings advance the clinical understanding of SUNCT and SUNA and suggest that their relationship with TN may represent` a clinical continuum between disorders. This view will hopefully open novel research directions towards a better understanding of these complex clinical entities.
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