Both the International Association for the Study of Pain (IASP) and International Headache Society (IHS) have suggested their own diagnostic criteria for TGN. 91 143 These are remarkably similar and highlight the sudden, explosive nature of the pain (Table 1). In further descriptions of the condition, both classi®cations allude to vascular compression, MS and tumours as known aetiological causes. The IASP classi®cation makes a distinction between TGN (including MS) and secondary neuralgias (caused by structural lesions and injuries, but not including MS), while IHS separates idiopathic TGN from the`symptomatic form' depending on the presence of a structural lesion; it is not quite clear if vascular compression quali®es as such. Neither approach includes reference to variant forms of TGN, which satisfy the diagnostic criteria but display additional features as well.

The likelihood of rupture of unruptured intracranial aneurysms that were less than 10 mm in diameter was exceedingly low among patients in group 1 and was substantially higher among those in group 2. The risk of morbidity and mortality related to surgery greatly exceeded the 7.5-year risk of rupture among patients in group 1 with unruptured intracranial aneurysms smaller than 10 mm in diameter.

Summary Twenty mature horses with typical headshaking of 2 week‐7 year duration were studied. Clinical examinations included radiography of the head and nasopharyngeal endoscopy. All were assessed at rest and at exercise, both before and after fitting an occlusive nasal mask, application of tinted contact lenses and the perineural anaesthesia of the infraorbital and posterior ethmoidal branches of the trigeminal nerve. Infraorbital anaesthesia had no effect in 6/7 cases but 11/17 (65%) cases showed a 90–100% improvement following posterior ethmoidal nerve anaesthesia. Tinted contact lenses had no apparent long‐term benefit, although 2 cases showed a transient improvement. We found no other evidence to suggest a photic aetiology in the current series of cases. Treatment regimens based on the results of the diagnostic investigative methods included sclerosis of the posterior ethmoidal branch of the trigeminal nerve. This was effective in some cases but the benefits were temporary. Cyproheptadine alone was ineffective but the addition of carbamazepine resulted in 80–100% improvement in 80% of cases. Carbemazepine alone was effective in 88% of cases but results were unpredictable at predefined dose rates. The positive response to carbamazepine, combined with the clinical features is consistent with involvement of the trigeminal nerve, particularly the more proximal branches such as the posterior ethmoidal nerve. Headshaking has some clinical features in common with trigeminal neuralgia in humans. As a result of the findings detailed in this paper, we conclude that a trigeminal neuritis or neuralgia may be the basis of the underlying aetiopathology of equine headshaking. Initial observations of the positive response of headshakers to carbamazepine therapy is encouraging. However, future studies will include a more detailed investigation of dosages, duration of effectiveness (in some cases it appears short‐lived) and other effects. In practice there is a realistic possibility of controlling but not curing headshaking with carbamazepine therapy at the present time. Other future investigations will include details of the functional anatomy of the trigeminal nerve and the role of the P2 myelin protein in headshaking and other neurological disease.

This is a large review of MVD, which confirms the long-term effectiveness of the procedure, and uniquely reflects patient's perception of the operation. Predictors of favourable outcome were shorter preoperative duration of TGN, older age at time of MVD, typical features, and vascular compression; moreover, complications, and previous neurodestructive procedures did not show significant effect on long-term pain relief. Satisfaction with MVD was exclusively related to long-term pain relief without medications.

The most important prognostic factor in determining recurrence was Simpson grading. There was no statistically significant impact of adjuvant radiotherapy on the recurrence of atypical meningiomas. Meta-analysis for the existing literature is needed.

The NeuroMate stereotactic robot in a frameless mode has sufficient accuracy for a range of functional neurosurgical procedures, including movement disorder surgery.

Until recently, the inability to demonstrate neurovascular compression of the trigeminal nerve preoperatively resulted in surgery being offered only in cases of severe trigeminal neuralgia (TGN), frequently after a prolonged trial of medical treatment and following less invasive procedures, despite the fact that posterior fossa microvascular decompression gives long-term pain relief in 80% to 90% of cases. To assess whether vascular compression of the nerve could be demonstrated preoperatively, high definition magnetic resonance tomographic angiography (MRTA) was performed in 50 consecutive patients, five of whom had bilateral TGN, prior to posterior fossa surgery. The imaging results were compared with the operative findings in all patients, including two patients who underwent bilateral exploration. Vascular compression of the trigeminal nerve was identified in 42 of 45 patients with unilateral symptoms and on both sides in four patients with bilateral TGN. In the last patient with bilateral TGN, neurovascular compression was identified on one side, and on the other side the compressing superior cerebellar artery was separated from the nerve by a sponge placed during previous surgery. There was full agreement regarding the presence or absence of neurovascular compression demonstrated by MRTA in 50 of 52 explorations, but MRTA misclassified four vessels compressing the trigeminal nerve as arteries rather than veins. In two cases, there was disagreement between the surgical and MRTA findings. In the first of these cases, surgery revealed distortion of the nerve at the pons by a vein that MRTA had predicted to lie 6 mm remote from this point. In the second patient, venous compression was missed; however, this patient was investigated early in the series and did not have gadolinium-enhanced imaging. In nine cases, MRTA correctly identified neurovascular compression of the trigeminal nerve by two arteries. Moreover, MRTA successfully guided surgical reexploration in one patient in whom a compressing vessel was missed during earlier surgery and also prompted exploration of the posterior fossa in two patients with multiple sclerosis and one patient with Charcot-Marie-Tooth syndrome, in whom neurovascular compression was identified preoperatively. It is concluded that MRTA is an extremely sensitive and specific method for demonstrating vascular compression in TGN. As a result, open surgical procedures can be recommended with confidence, and microvascular decompression is now the treatment of choice for TGN at the authors' unit. They propose MRTA as the definitive investigation in such patients in whom surgery is contemplated.

Neuronavigation enables safe, accurate surgery, and may ultimately reduce complications and improve outcome. Electromagnetic technology allows frameless, pinless, image-guided surgery, and can be used in all procedures for which neuronavigation is appropriate. This technology was found to be particularly advantageous compared with other technologies in cases in which freedom of head movement was helpful. Electromagnetic neuronavigation was therefore well suited to CSF diversion procedures, awake craniotomies, and cases in which rigid head fixation was undesirable, such as in neonates. This technology extends the application of neuronavigation to routine shunt placement and ventricular catheter placement in patients with traumatic brain injury.