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The operative microscope in modern neurosurgery

Having developed with the times, the operative microscope is an essential piece of equipment in the modern neurosurgical theatre

The oldest neurosurgical procedure, trephination, first appeared during the Neolithic period. Modern understanding of optic law was started by Arabic scientists, between AD 1027 and 1040. Two hundred years later, in western countries, Roger Bacon published his works on optics. The possibility of magnification using a serial array of lenses was then later described by Dominican monks in Italy at the end of the 14th century.

A microscope is an inversed telescope, and the lens array was developed by Hans Lippershey, Zacharias Janssen and Hans Janssen in 1590. In 1686, Italian inventor and scientist Giuseppe Campani (1635 to 1715) described the first recorded use of a microscope to analyse wounds, sores and anatomic specimens in medical and surgical settings.

The industrial production of microscopes was initiated by Carl Zeiss in the mid 1800s in collaboration with Ernst Carl Abbe, Professor of Physics at Jena University, as well as a team of surgeons. Initially, an operating microscope was used by an otologist at the University of Stockholm, Carl Olf Nylen (1892 to 1978), to operate on a patient with inner ear disease in 1921, instead of using an operating loupe.

In 1957, at the University of Southern California, Theodor Kurz removed a benign, encapsulated Schwann cell tumour of the cranial nerve VII. This was the first use of the microscope in neurosurgery. Since then, the operating microscope has become, through trial and error, and refinement and collaboration with neurosurgeons, an important device in human neurosurgery.

Operating microscopes have improved greatly since they were first introduced. More sophisticated devices have also entered the human neurosurgical theatre, which have good magnification, good illumination without significant aberration or production of excessive heat and a great internal stability, which allows operational flexibility.

First and foremost, although the learning curve associated with the use of the microscope has been steep and requires time, it is naturally more than just using endoscopic associated magnification tools, because there is direct visual control of the instrumentation.

The possibility to have magnifications up to x10, with a good depth of field, allows a more natural three-dimensional vision. In fact, compared to loupes where the magnification and the working distance is fixed, surgical microscopes allow multiple different magnifications, maintaining constant working distances and in turn, leading to excellent flexibility and versatility during surgical procedures.

During neurosurgery, for example, low magnification is used during the drilling of the vertebral lamina or the skull and to ensure that the whole surgical field is clean before suturing the muscle layers.

FIGURE 1 Microphotography of a durectomy performed in a pug after removal of a subarachnoid diverticulum under microscopic control. The holding sutures are of a 6-0 suture (0.07mm in diameter). Note the clarity of visualisation of delicate structures, such as spinal vessels and the spinal cord itself
FIGURE 1 Microphotography of a durectomy performed in a pug after removal of a subarachnoid diverticulum under microscopic control. The holding sutures are of a 6-0 suture (0.07mm in diameter). Note the clarity of visualisation of delicate structures, such as spinal vessels and the spinal cord itself

Higher magnification is used while dealing with delicate structures such as the spinal cord (Figure 1) or brain. The higher magnification, coupled with a good depth of view and stable three-dimensional vision, increases the security and safety when manipulating microsurgical instruments near the nervous tissue. Although time of surgery initially might be prolonged due to the learning curve, no difference in rate of post-operative infection was observed during multiple studies in human neurosurgery.

In our experience, the post-operative infection rate has also not been changed. In human neurosurgery, although single macrodiscectomy (discectomy without use of operative microscope) and microdiscectomy in the hands of extremely experienced surgeons does not change the short and medium (one year) outcomes, in general, their use allows a lower rate of post-operative complications (ie dural tears), better patient satisfaction, lower pain scores and functional outcome comparable with surgical loupes.

Importantly, modern operative microscopes are no longer fixed on the patient, but either to the ceiling or to a tripod, allowing multiple spatial configuration to ensure a perfect vision of the surgical field. This has also had a positive outcome on the health and well-being of the surgeons. A 2013 study found that for nearly 85 percent of the time spent operating, surgeons have asymmetrical non-neutral head-neck postures, even further exaggerated when wearing loupes or headlamps. These postures determine higher biomechanical loading of the cervical spine, and are recognised factors for occupational health disease, such as headache and chronic neck pain.

FIGURE 2 It is possible for two users to have a normal posture during the procedure and to work in the same small surgical approach without interference of delicate structures, such as spinal vessels and the spinal cord
FIGURE 2 It is possible for two users to have a normal posture during the procedure and to work in the same small surgical approach without interference of delicate structures, such as spinal vessels and the spinal cord

From a training point of view, microscopes with multiple binoculars allow two or more surgeons to operate simultaneously in the same restricted operative field without reciprocal interference (Figure 2). Moreover, with adding high resolution cameras, it is possible to project and record the surgery performed with a clear vision and high definition. The latter is of utter importance in the context of training and teaching environments.

Neurosurgical microscopes are not often used in veterinary medicine. In the context of veterinary neurosurgery, we strongly believe that the operative microscope is an essential piece of equipment when dissecting close to the brain or spinal cord in small animals. The lesson learnt by constantly using the operating microscope is that we have already improved our surgical abilities to deal with complex spinal and brain surgeries. We are confident that the use of this tool will continue to promote progress to the benefit of our pets that deserve the best treatment available for their neurological conditions.

Spinal cord decompression due to intervertebral disc extrusion in a 1kg chihuahua

Further reading

Brogna, C., Millesi, M., Fiengo, L., Richardson, M., Bhangoo, R., Ashkan, K. and Türe, U. (2018) Commentary: Giuseppe Campani (1635-1715, Rome, Italy): the first use of a microscope in medicine and surgery. Neurosurgery, 82, E58.

Dolera, M., Malfassi, L., Marcarini, S., Mazza, G., Sala, M., Carrara, N., Vailati Facchini, R. and Finesso, S. (2015) Hydrated nucleus pulposus extrusion in dogs: correlation of magnetic resonance imaging and microsurgical findings. Acta Veterinaria Scandinavica, 57, 58.

Nimbarte, A. D., Sivak-Callcott, J. A., Zreiqat, M. and Chapman, M. (2013) Neck postures and cervical spine loading among microsurgeons operating with loupes and headlamp. IIE Transactions on Occupational Ergonomics and Human Factors, 1, 215-223.

Uluç K., Kujoth, G. C. and Başkaya, M. K. (2009) Operating microscope: past, present, and future. Neurosurgical Focus, 27, E4.

A full list of references is available on request

Lorenzo Golini, DVM, MSc, Dip ECVN, MRCVS, is an RCVS specialist in Veterinary Neurology and has completed residency training in Neurology and Neurosurgery at the University of Zurich. He holds the European Diploma in Veterinary Neurology and has a masters degree in Behavioural Medicine.

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Massimo Mariscoli, DVM, Dip ECVN, MRCVS, graduated from the University of Bologna in 1990. After completing a three-year residency programme in Veterinary Neurology and Neurosurgery at the University of Bern, Massimo passed the Diploma of the European College of Veterinary Neurology.

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Luca Motta, DVM (Hons), Dip ECVN, MRCVS, graduated in 2007 from the University of Perugia. After moving to England, he completed an internship programme in Small Animal Medicine and Surgery, and began a European College of Veterinary Neurology (ECVN) approved residency. Luca was awarded the ECVN Diploma in 2012.

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