the art of neuromonitoring

in spine surgery


Neuromonitoring in spine surgery

Second only to the brain, the spinal cord contains the most important neural structures of the central nervous system. These include the descending motor nerves that mainly carry impulses from the brain to the muscles, as well as the ascending sensory pathways that transmit information from the peripheral sensory organs to the brain. There is a general distinction between neuromonitoring efferent motor pathways via EMG (electromyography) and monitoring afferent (ascending) pathways using somatosensory evoked potentials (SEP). In complex surgical scenarios, a combination of the different methods (modalities) is required, i.e. taking measurements simultaneously.Our AVALANCHE® SI neuromonitor in the 8-channel version is capable of performing EMG, SEP (median and tibial nerve) and MEP, which permits the reliable assessment of nerves in the spinal cord during operation. This is not only reassuring for the operating team, but actually improves patient safety.


Neuromonitoring can be used e.g. in diskectomy, scoliosis and root decompression surgery, during the resection of spinal tumours or for inserting pedicle screws.


monitoring critical proximity to motor pathways

The performance features of the AVALANCHE® SI EMG neuromonitor is especially adapted to the needs of spinal cord surgery and helps the surgeon to recognize motor neural pathways and test their function in each stage of the operation. When measuring electromyograms (EMG), neuronal structures in the operation site are electrically stimulated and transmitted to the peripheral muscles as action potentials. These are then picked up and measured by electrodes and visualized on the neuromonitor. Continuous EMG recording in several muscles simultaneously enables surgeons to respond immediately when they come critically close to motor neural pathways and signal activity increases.

In intermittent stimulation, the surgeon uses a hand-held probe to apply minute electrical impulses to tissue, which triggers the muscle action potential (MUAP) in the target muscle - depending on the surgery site - in arms or legs. If the tip of the probe comes close enough to a nerve and the neural pathway is intact, the surgeon will be alerted to the muscle action potential by an unmistakable acoustic and visual signal.


Pedicle Screw Testing

Pedicle screw monopolar ball probe:

Specific monopolar stimulation probes are available for the insertion of pedicle screws. These permit stimulation within the bore hole itself or through surgical instruments during the drilling and the screwing process. If the stimulation results in an increased signal activity on the neuromonitor, caution is advised - the bore hole, the screw or the drill come too close to the nerve. Thus, monopolar probes can assist in the early recognition of damage to the pedicle wall and ensure before the end of the operation that the screws are in place and functionality is checked.


For the monitoring of ascending pathways, in particular in surgery to straighten scoliosis

To ensure that changes that could result in post-operative neurological deficits, somatosensory evoked potentials (SEPs) are continually measured. Signals picked up in real time are compared to the normal signal recorded just after anaesthesia was induced - the baseline signal. The signal generated by electrical stimulation of the median nerve at the wrist or at the tibial nerve at the foot is acquired as an SEP cortically or subcortically and shows typical changes in amplitude and latency. These alert to potential or actual threats for the nerve during operation.

An increase in latency usually suggests that there are changes in the conduction velocity of axons, whereas a drop in amplitude is caused by a change in the numbers of excited neural fibres and a change in synchronicity in stimulus conduction. It is thus possible to monitor sensory afferents running across the operation site.


For the functional check of central motor pathways

Motor evoked potentials (MEPs) are a particular form of evoked potentials, measured through an EMG. They are triggered by transcranial or direct cortical stimulation, and the response signals are picked up at the corresponding extremity muscles. This enables the surgeon to quickly assess the state and functionality of the spinal cord.

Magnetic MEP stimulation does not seem viable in the operating theatre, whereas MEP recording with high-voltage stimulation has established itself as an important and reliable monitoring method in spinal surgery. It is usually used to complement EMG recording, directly stimulating motor nerves.

Stimulation probes

Electric stimulation of nerves and neuronal structures

The choice is yours: Bipolar or monopolar, conventional or minimally invasive, with or without microscope. Reusable or disposable accessories -

Our range offers a matching solution for virtually all situations.

Our stimulation probes have been made with special attention to ergonomics.

Quality made in Germany by Dr. Langer Medical.



Colour-coded needle electrodes for recording and stimulation

Whether one or several channels are required for the recording of EMG or EP signals or nerves and muscular tissue are to be stimulated, needle electrodes by Dr. Langer Medical GmbH will give you ample choice for neuromonitoring.

Various lengths, shapes and geometric arrangements as well as a palette of colours to suit your particular application purposes are available - the choice is yours.

Fields of application