Intracranial pressure waves generated by high-energy short laser pulses can cause morphological damage in remote areas: comparison of the effects of 2.1-micron Ho:YAG and 1.06-micron Nd:YAG laser irradiations in the rat brain.
OBJECTIVE
Histological effects of 2.1-micron Ho:YAG and 1.06-micron Nd:YAG laser pulses were compared in the rat brain, with special regard to areas remote from the irradiated site.


METHODS
Laser pulses were delivered through a 0.6-mm glass fiber, the tip of which was either introduced into the caudate nucleus (application mode I), or held at a 2-mm distance above the exposed intact dura. In the latter case, the space between the dura and the fiber tip was filled either with physiological saline (application mode II) or with air (application mode III).


RESULTS
In application modes I and II, but not in application mode III, Ho:YAG laser pulses of 1.5 J and 200 microseconds, but not Nd:YAG laser pulses with the same parameters, immediately caused morphological damage to a considerable number of neurons and axons randomly distributed among apparently normal ones in certain areas remote from the irradiated site. A decrease in the energy and an increase in the length of the pulses lowered the incidence of the remote morphological damage.


CONCLUSIONS
This novel finding may impose limits on the application of Ho:YAG lasers in human endoscopic neurosurgery.
Czurkó
A
A
Department of Neurosurgery, University Medical School of Pécs, Hungary.
Tóth
Z
Z
Dóczi
T
T
Gallyas
F
F
D000818:Animals; D001812:Blood-Brain Barrier; D001921:Brain / Q000473:pathology*; D004724:Endoscopy / Q000009:adverse effects; D005260:Female; D006801:Humans; D019586:Intracranial Hypertension / Q000209:etiology / Q000473:pathology*; D007427:Intracranial Pressure; D053685:Laser Therapy / Q000009:adverse effects*; D008297:Male; D019635:Neurosurgical Procedures / Q000009:adverse effects; D051381:Rats; D017208:Rats, Wistar