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Edoardo Mazzucchi, Andrei Brinzeu, Patrick Mertens, and Marc Sindou

Pain in patients with cancer is a major problem, and sometimes it is necessary to surgically interrupt pain pathways to effectively control refractory pain. Surgical lesion of the dorsal root entry zone (DREZ) was first performed in 1972 for the treatment of pain related to a Pancoast-Tobias tumor. The rationale of DREZotomy is to preferentially interrupt the nociceptive inputs in the lateral part of the DREZ and the ventrolateral (excitatory) part of the dorsal horn. Microsurgical DREZotomy is one technique for DREZ lesioning that is suited for tailored control of pain in patients in good general condition who are experiencing pain in a well-defined territory.

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Marc Guenot, Jean-Michel Hupe, Patrick Mertens, Alan Ainsworth, Jean Bullier, and Marc Sindou

Object. In this paper the authors report on the conception and adjustment of a microelectrode used to obtain unitary recordings in the human spinal cord.

Methods. To overcome the difficulties related to intraoperative pulsations of the spinal cord, the authors opted to use a floating microelectrode. Because the recordings are obtained most often from spontaneous activities, it is difficult, with a single microelectrode, to separate spikes from electrical artifacts that are related to the switching of devices. Consequently, the authors designed a dual microelectrode made of two tungsten-in-glass—attached microelectrodes separated by 300 µm. Because the two electrodes cannot obtain recordings in the same neuron, it is possible to distinguish unambiguously spikes (recorded on one tip) from electrical artifacts (recorded simultaneously on the two tips). The dual microelectrode is 2 cm long, with a 20-µm tip length, and 800 to 1200—Ohms impedance. This microelectrode can be implanted “free hand,” in the dorsal horn, by using a microsurgical forceps under a surgical microscope. The data analysis is performed off-line with spike sorter hardware.

In the dorsal horns in 17 patients who were selected to undergo a dorsal root entry zone (DREZ) rhizotomy to treat various pathological conditions, unitary recordings were obtained using this double microelectrode. The authors recorded 57 neurons in good conditions of stability and isolation.

Conclusions. The microelectrode described in this paper was successfully used to obtain recordings in neurons in more than 85% of the patients. This simplified, floating double microelectrode can therefore be considered for use in microsurgical DREZ rhizotomy to obtain unitary recordings in the human spinal dorsal horn.

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Joseph Maarrawi, Patrick Mertens, Jacques Luaute, Christophe Vial, Nicole Chardonnet, Maryse Cosson, and Marc Sindou


To manage refractory upper-limb spasticity, selective peripheral neurotomy (SPN) is proposed when the spastic muscles to be treated are under the control of a single or a few peripheral nerves. The aim of this study was to assess prospectively the long-term effects of SPN.


Thirty-one patients with disabling upper-limb spasticity were selected by a multidisciplinary team using clinical, analytical, and functional scales as well as nerve block tests for assessment. Sixty-four SPNs were performed at the level of the musculocutaneous (15 SPNs), the median (25 SPNs), and the ulnar (24 SPNs) nerves. Results of a long term follow up (mean 4.5 years) showed statistically significant improvement on 1) analytical assessment (p < 0.01): resting position, active amplitude, and motor strength; 2) Ashworth Scale scoring (p < 0.01); 3) hand function assessment (p < 0.01); and 4) rating of daily activities. Four patients with severe painful spasticity experienced complete pain relief after surgery. On the basis of a Visual Analog Scale ranging from 0 to 100, the mean degree of patient satisfaction was 61.5. Complications occurred in five patients (15%): two postoperative hematomas, one (temporary) hypesthesia, and one transient paresia of the wrist and finger flexors.


Selective peripheral neurotomy leads to long-term satisfactory improvement in function and/or comfort with a low morbidity rate in appropriately selected patients suffering from severe harmful spasticity of the upper limb that has been refractory to conservative therapy. Patients must be selected after complete assessment by a multidisciplinary team.

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Patrick Mertens, Chantal Ghaemmaghami, Lionel Bert, Armand Perret-Liaudet, Marc Guenot, Hussein Naous, Laurent Laganier, Roger Later, Marc Sindou, and Bernard Renaud

✓ The aim of this study was to develop, for the first time in the human spinal dorsal horn (DH), an in vivo method for the study of amino acids (AAs).

A microdialysis technique was used to sample AAs in the extracellular fluid of the DH apex in eight patients in whom surgery in the dorsal root entry zone (DREZ) was performed. Before making microsurgical lesions, specific concentric-type microdialysis probes were implanted over a 60-minute period in the DREZ and directed to the DH apex (10 implantations). The AA concentrations in the dialysates were determined using high-performance liquid chromatography with fluorescence detection. The concentrations of excitatory AAs (glutamate and aspartate) and inhibitory AAs (γ-aminobutyric acid and glycine) decreased and were stabilized by 45 minutes after probe implantation, whereas the levels of nonneurotransmitter AAs (alanine and threonine) were not stabilized at 60 minutes. The ability of the probe to track the changes of extracellular AAs was demonstrated. Neither intra- nor postoperative microdialysis-related complications were observed (with a follow up of 18 months).

The present study demonstrates that microdialysis can be performed safely in the human DH during DREZ lesioning. Despite technical and analytical limitations related to the intraoperative conditions, this technique offers new possibilities for clinical research on neurotransmitters involved in some relevant pathological states, especially in chronic pain and spasticity.