Tissue welding using a low energy microsurgical CO2 laser.

A low energy, CO2 laser adapted specifically for microsurgery can be used to assist in anastomosis by "welding" tissue through thermal coagulation. Which tissue constituents contribute to the bond are not known, and different constituents may be important in welding different organs.

Laser-assisted microsurgical anastomosis.

A low power carbon dioxide laser was used to perform 212 end-to-end laser-assisted microvascular anastomoses (LAMA) of femoral arteries (mean diameter, 1.2 mm) in Sprague-Dawley rats. Eighty-two conventional microvascular suture anastomoses (CMSA) utilizing 10-0 monofilament interrupted sutures were done for comparison of techniques and wound healing. The mean duration of each anastomosis procedure was 16 minutes for the LAMA repairs, compared to an average of 27 minutes for the CMSA repairs (P less than 0.05). All anastomoses were patent at the completion of the procedure. Each laser-assisted anastomosis required an average of seven intermittent laser exposures of 0.1 to 0.3 seconds each with approximately 80 mW of CO2 (wavelength = 10.6 micron) radiation at a spot size of 150 micron. A patency rate of 95% was obtained on the LAMA vessels (202 of 212) compared to 96% for the CMSA repairs (79 of 82). A total of 14 aneurysms were noted in the LAMA group (7%) compared to 11 in the CMSA (13%). All aneurysms were in patent vessels. Histological analysis indicates that the progression of wound healing of LAMA and CMSA anastomoses follows similar paths chronologically and morphologically with increased scar tissue formation around the suture. Scanning electron microscopy confirms the comparable luminal healing of the LAMA and CMSA vessels, with complete reendothelialization occurring by 3 weeks postoperatively. The tensile strength of the LAMA repair, although low immediately after operation, is comparable to that of the intact artery at 21 days. These findings suggest that a low energy carbon dioxide microsurgical laser has potential beneficial clinical application for anastomosis of small vessels.

Carbon dioxide laser stapedotomy: a histopathologic study.

The effect of carbon dioxide electromagnetic radiation on biological tissues is thermal. The heat generated from vaporization dissipates into the surrounding tissues and can produce alterations of structure and function. Carbon dioxide laser fenestrations were performed in the footplates of 11 cat ears. Morphologic changes included discoloration and reactive hemorrhage in the saccular wall and disruption of the saccular and utricular walls. The clinical consequences of these findings and the role of the carbon dioxide laser in laser stapedotomies for patients with otospongiosis remain unresolved.

Carbon dioxide laser stapedotomy. Thermal effects in the vestibule.

Small-fenestra stapedotomy has recently been popularized in efforts to reduce the incidence of sensorineural hearing loss following stapes surgery for otospongiosis. Lasers have been advocated as a tool to fenestrate the stapes footplate. Conversion of radiant energy from the laser into heat in the vestibule represents the greatest potential risk to the inner ear. Using a carbon dioxide laser with a focal point of 150 microns at 300 mm, fenestrations of the stapes footplate were performed in a series of 14 anesthetized cats. The laser power output ranged from 0.47 to 3.05 W, with pulse durations of 0.2 and 0.5 s. Resultant temperature elevations in the vestibule, measured by a thin-wire thermocouple, ranged from 0 to 4.4 degrees C (0 to 8 degrees F) and directly correlated to wattage and duration of the laser-beam pulse. Temperature changes could be reduced by use of lower wattage, shorter pulse duration, timed intervals between pulses, and convection cooling of the promontory.

Laser-assisted microvascular anastomoses: angiographic and anatomopathologic studies on growing microvascular anastomoses: preliminary report.

A low-powered carbon dioxide laser was used to perform end-to-end anastomoses of growing femoral arteries (mean diameter 1.6 mm) in miniature swine. Five microvascular conventional anastomoses were performed with 10-0 monofilament interrupted sutures. Nine laser-assisted vascular anastomoses were performed. The mean duration of each anastomosis was 30 +/- 3 minutes for the conventional anastomosis and 20 +/- 2 minutes for the laser-assisted vascular anastomosis (p less than 0.05). All anastomoses were patent at the completion of the procedure. Each laser-assisted anastomosis required an average of eight laser pulses of 2 to 4 seconds. After 13 weeks the external diameters of the conventional anastomoses were 1.8 mm (+15%), while the laser-assisted anastomoses averaged 3.0 mm (+81%) (p less than 0.05). All nine laser-assisted anastomoses were patent, functional, and free of stenosis compared with one out of five conventional anastomoses. Histologically the laser induced minimal or no fibrosis, allowing normal physiologic healing and growth patterns. Electron microscopy confirmed that the integrity of the arterial layers had been restored. These findings suggest that a low-energy carbon dioxide laser has potential clinical application for anastomosis of small growing vessels.

Differential facial nerve function in tumors of the internal auditory meatus.

Fifty-five consecutive cases of neoplastic involvement of the internal auditory meatus resulting in ipsilateral retrocochlear auditory dysfunction were reviewed. The majority of these tumors (89%) were solitary schwannomas of the eighth nerve. Eleven percent were other tumors. Preoperative facial paralysis was unusual in eighth nerve schwannomas (6.1%) and much more common in other tumors (66.6%). These data tend to suggest that facial paralysis preoperatively increases the probability that the tumor is other than an eighth nerve schwannoma. Furthermore, facial paralysis resulting from an eighth nerve schwannoma indicates a poorer prognosis for ultimate facial nerve function. The small numbers in this series, though far from conclusive, suggest that normally functioning facial nerves may be infiltrated by eighth nerve schwannomas. Failure of eventual recovery of facial nerve function in the postoperative period may suggest tumor infiltration.

Diagnosis and treatment of spontaneous cerebrospinal fluid otorrhea.

Two consecutively operated-on adult cases with spontaneous cerebrospinal fluid otorrhea were reviewed. Three meningoencephaloceles through tegmental defects were found. Each cele was peduculated through a small dural dehiscence partially obstructed by herniated brain. The otic capsule was normal in both cases. Bipolar cautery was used to reduce the size of the meningoencephalocele and to allow this tissue to assist in the closure of the defect. Conchal cartilage was placed through the tegmental defect to act as a self maintaining intracranial repair of the bony dehiscence. These cases and the literature suggest that fistulization of dura is more frequently the cause of spontaneous cerebrospinal fluid otorrhea in adults than is a defect in the otic capsule. Thus, direct surgical inspection of these areas is required.

Clinical correlates of neoplastic involvement of the eight cranial nerve in man.

This study of 25 cases of benign neoplastic involvement of the eighth nerve in man suggests: (1) Eighth nerve auditory dysfunction and minimal structural change in the internal auditory canal are the earliest reliable signs leading to tumor detection. (2) "Early" detection does not mean "small" tumor. (3) Schwannomas tend to grow more slowly in the elderly patient. (4) Compression and displacement of viable axons may be the primary pathophysiology of dysfunction.

Symptomatic cysts of the telencephalic choroid plexus.

Symptomatic cysts of the telencephalic choroid plexus are rare. This is a paediatric problem, with the oldest patient being 10 years old. Pertinent cases from the literature are reviewed. The case of a 9 year old girl with suboccipital headaches made more severe by lying on her right side or on her abdomen is discussed. Physical examination was within normal limits except for evidence of early papilloedema. The cerebrospinal fluid pressure was normal, and the protein was not elevated (32 mg/100 ml.). The brain scan showed a left frontoparietal mass near the midline, and the electroencephalogram was abnormal. The pneumoencephalogram demonstrated a mobile, pedunculated mass in the left trigone which approached the foramen of Monro when the patient assumed the head-erect position. A transcallosal approach was used and the cyst was easily removed. Postoperatively the patient has done well and is currently asymptomatic and without headaches. The significance of the presenting symptoms, the cerebrospinal fluid and brain scan findings, as well as the surgical approach, are discussed.