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Letter to the Editor

Posterior spinal artery

Philippe Mercier

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Henri-Dominique Fournier, Philippe Mercier, and Philippe Menei

Object. Because central nervous system white matter exerts a powerful inhibitory effect on axonal growth, implantation of nerve grafts or rootlets into the cervical spinal cord following ventral root avulsion injury should, ideally, be performed directly through the ventral root exit zone (VRExZ), which is located near the anteromedial aspect of the anterior horn; the grafts/rootlets should not be implanted into the white matter of the lateral cord. This is not possible when using a conservative posterior approach. Therefore, the authors have studied the anatomy encountered when using the anterolateral approach and evaluated the technique in the particular case of avulsed ventral nerve roots. They also present a case illustration of the procedure, which is used currently in their department.

Methods. Anterior access to the rootlets is obtained using a lateral interscalenic approach; the vertebral artery is exposed and mobilized, and oblique drilling of the vertebral bodies (VBs) is performed. Because the articular processes and half of the VBs are preserved, fusion is not required.

The approach allows the surgeon to expose the anterior aspect of the cervical dura and the entire length of the emerging spinal nerves. The anterior aspect of the dura is opened at the desired levels for VRExZ exposure, and the position is ideal for implantation of the graft/rootlets. The interscalenic dissection is mandatory so that the lesions of the supraclavicular plexus can be evaluated and repaired. If necessary, the anterior approach allows for exploration of the infraclavicular plexus during the same procedure.

Conclusions. The use of a true anterior approach to the ventral rootlets appears to be a valuable and appropriate approach that avoids extensive laminectomy/facetectomy while reimplantation is performed through the anterolateral sulcus itself. In this approach, however, reimplantation of dorsal roots into the spinal cord remains impossible.

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Raeph Fardoun, Yves Adam, Philippe Mercier, and Gilles Guy

✓ A case of a tentorial arteriovenous aneurysm is reported in a 54-year-old man. This malformation, fed by branches of the external carotid artery, was drained exclusively by a parieto-occipital cortical vein. The rupture of this vein was responsible for the presenting intracerebral hematoma.

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Ala Birca, Claude Mercier, and Philippe Major

Tuberous sclerosis complex (TSC) is associated with the potential development of benign hamartomas, including subependymal giant cell astrocytomas (SEGAs). Intracranial hypertension can be caused by SEGAs due to their propensity to block the foramen of Monro. The traditional management approach is to monitor SEGAs with periodic neuroimaging and to resect those that exhibit serial growth and/or cause clinical signs of intracranial hypertension. Recent observations suggest that rapamycin therapy may induce partial regression of SEGAs, therefore providing a potential alternative to resection. The authors present the case of an 8-year-old girl with bilateral SEGAs that led to progressive hydrocephaly and incipient signs of papilledema. Three months after initiating rapamycin therapy, the SEGAs exhibited significant reduction in size (82.6% on the left and 46.7% on the right), and the lesions remained stable 5 months later. Compared with previous case reports, similar or even greater antitumor efficacy was achieved with much lower trough levels of rapamycin (10–15 compared with 3.3–4.5 ng/ml, respectively). The authors discuss various aspects of rapamycin therapy and address unresolved issues that highlight the need for further prospective clinical trials.

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Didier Scavarda, Philippe Major, Anne Lortie, Claude Mercier, and Lionel Carmant


Ischemic cerebral vascular accidents (CVAs) in children result in epilepsy in 25% of patients, which is refractory in 7% of cases. Repeated seizures worsen the global and cognitive prognosis of these patients. To evaluate the prognosis of epilepsy and cognitive development in children with refractory seizures following a CVA, the authors retrospectively studied the effectiveness of periinsular hemispherotomy in the treatment of these patients.


Between March 1995 and November 2007, 8 children who suffered from stroke-induced refractory epilepsy underwent a periinsular hemispherotomy. All patients' charts were reviewed in a retrospective manner. Age at the time of the CVA, imaging studies, cause of the ischemic event, onset of the first seizure, patient's handedness, the extent of the parenchymal damage, electroencephalography findings, type of epileptic seizures, number of seizures per day, number of antiepileptic medications, preoperative neuropsychological evaluation, and surgical outcome with regard to the patient's seizure activity were analyzed.


There were 7 boys and 1 girl in this study. The mean age at stroke was 23 months (range birth–5 years). The mean age at onset of epilepsy was 22 months (range 0–60 months). The mean age at the time of the hemispherotomy was 7 years (range 54–130 months). The average delay prior to the hemispherotomy was 5 years and 3 months (range 23–115 months). Prior to surgery, the average number of seizures per day was 35 (range 5–100). The average number of antiepileptic medications introduced before the hemispherotomy was 8 (range 6–12). Six patients required only 1 surgical intervention and 2 necessitated 2 separate operations:1 underwent a 2-staged hemispherotomy and the other underwent a prior callosotomy. There were no reported surgical complications in this series. Seven children are seizure free. However, the remaining child, after a 3.5-year disease-free interval, has recently started having seizures. No child demonstrated an improvement in neuropsychological evaluation.


The periinsular hemispherotomy must be considered an alternative in the therapeutic approach to stroke-induced pediatric refractory epilepsy. It is effective in controlling seizure activity. The authors believe the delay before hemispherotomy must be shortened in children with post-CVA refractory epilepsy.

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Woojin Joo, Philippe Mercier, Shiva Kheradmand, Peyman Shirani, Ahmed Sarhan, Samer K. Elbabaa, and Randall C. Edgell

This case report describes the use of the Micro Vascular Plug (MVP) system in a mural-type vein of Galen aneurysmal malformation, resulting in successful occlusion of the cerebrovascular fistula. This result was confirmed with immediate cessation in blood flow and 6-month follow-up angiography. The unique characteristics of the MVP provide potential advantages over current embolic techniques for occlusion of high-flow, fistulous, intracranial vessels such as those seen in the vein of Galen aneurysmal malformation, and may represent a valuable addition to the currently available options.

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Aurore Sellier, Nathan Beucler, Christophe Joubert, Nicolas Desse, and Arnaud Dagain

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Anne Pasco, Francine Thouveny, Xavier Papon, Jean-Yves Tanguy, Philippe Mercier, Christine Caron-Poitreau, and Denis Herbreteau

✓ The posterior inferior cerebellar artery (PICA) is known to be very variable, and some of its anatomical variations can explain ischemic complications that occur during endovascular treatment of aneurysms. The authors report two cases of anatomical variation of the PICA that they have called its double origin, one of which gave rise to an aneurysm.

The first patient was a 36-year-old man who presented with a subarachnoid hemorrhage related to the rupture of a PICA aneurysm. The aneurysm was treated by the endovascular route. Selective and superselective studies showed that the PICA origin was low on the fourth segment of the vertebral artery (VA). The aneurysm was located on an anastomosis between the PICA and a small upper arterial branch originating from the VA. Embolization was performed through the small branch with no problem, but a lateral medullary infarct followed, probably due to occlusion of the perforating vessels. The same anatomical variation was incidentally discovered in the second patient.

To the authors' knowledge, neither this anatomical variation of the PICA nor the aneurysm's topography have been previously described angiographically. This highlights the role of angiography in pretreatment evaluation of aneurysms especially when perforating vessels or small accessory branches that are poorly visualized on angiographic studies are concerned, as in the territory of the PICA. Anatomy is sometimes unpredictable, and the surgeon must be very careful when confronted with these variations because they are potentially dangerous for endovascular treatment.

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Georgios Alexopoulos, Nabiha Quadri, Maheen Khan, Henna Bazai, Carla Formoso Pico, Connor Fraser, Neha Kulkarni, Joanna Kemp, Jeroen Coppens, Richard Bucholz, and Philippe Mercier


Penetrating brain injury (PBI) is the most lethal of all firearm injuries, with reported survival rates of less than 20%. The projectile trajectory (PT) has been shown to impact mortality, but the significant lobar tracks have not been defined. The aim of this retrospective case-control study was to test for associations between distinct ballistic trajectories, missile types, and patient outcomes.


A total of 243 patients who presented with a PBI to the Saint Louis University emergency department from 2008 through 2019 were identified from the hospital registry. Conventional CT scans combined with 3D CT reconstructions and medical records were reviewed for each patient to identify distinct PTs.


A total of 65 ballistic lobar trajectories were identified. Multivariable regression models were used, and the results were compared with those in the literature. Penetrating and perforating types of PBI associated with bitemporal (t-statistic = −2.283, p = 0.023) or frontal-to-contralateral parietal (t-statistic = −2.311, p = 0.025) projectile paths were universally found to be fatal. In the group in which the Glasgow Coma Scale (GCS) score at presentation was lower than 8, a favorable penetrating missile trajectory was one that involved a single frontal lobe (adjusted OR 0.02 [95% CI 0.00–0.38], p = 0.022) or parietal lobe (adjusted OR 0.15 [95% CI 0.02–0.97], p = 0.048). Expanding or fragmenting types of projectiles carry higher mortality rates (OR 2.53 [95% CI 1.32–4.83], p < 0.001) than do nondeformable missiles. Patient age was not associated with worse outcomes when controlled by other significant predictive factors.


Patients with penetrating or perforating types of PBI associated with bitemporal or frontal-to-contralateral parietal PTs should be considered as potential donor candidates. Trauma patients with penetrating missile trajectories involving a single frontal or parietal lobe should be considered for early neurosurgical intervention, especially in the circumstances of a low GCS score (< 8). Surgeons should not base their decision-making solely on advanced patient age to defer further treatment. Patients with PBIs caused by nondeformable types of projectiles can survive multiple simultaneous intracranial missile trajectories.