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  • The two most common complications following surgery of the cerebellopontine angle are CSF leakage and cranial nerve palsies. Less commonly encountered complications include bacterial and aseptic meningitis, wound infection, hydrocephalus and haemorrhage.

    CSF leakage most often results from a mastoid air cell opened during the craniectomy or during the drilling of the posterior wall of the internal auditory canal. Fluid then drains from these cells into the middle ear and through the eustachian tube down into the pharynx or the nose. A CSF leak may not present immediately, but may start several days following surgery when the patient is mobilized. A small drainage of clear fluid occurring in the immediate postoperative period may represent fluid that has accumulated in the mastoid air cells at the time of surgery. A drainage that persists longer than 24 h, or one that worsens with a Valsalva manoeuvre, is more likely to be a true CSF leak and should be managed aggressively. This includes placement of a lumbar drain, administration of prophylactic antibiotics, and daily measurement of CSF cell counts. After 5 to 7 days, the drain is removed and, in usual conditions, the leakage does not recur. If that is unsuccessful, patients usually undergo a mastoidectomy for obliteration of the air cells and the eustachian tube without re-exploring of the surgical site.

    A CSF leak can also occur from the wound. This is usually a result of poor wound-healing, hydrocephalus, or wound infection. The treatment of the leak actually begins at the time of the initial incision. A clean, sharp incision and careful handling of the wound edges is important. Also, the surgeon must obtain a meticulous closure of the fascial layers, especially along the inferior aspect of the wound overlying the mastoid tip, where clear fascial planes are not always present. In spite of good technique, a CSF leak may still occur if intracranial pressure is elevated or if a wound infection develops. In patients with hydrocephalus, simple stitching of the wound seldom solves the problem unless the hydrocephalus is treated simultaneously. If there is no underlying infection, a ventriculoperitoneal shunt is placed. If the patient has a concurrent infection, a ventriculostomy is placed until the infection has cleared and a shunt can be inserted.

    Dysfunction of cranial nerves V, VII, VIII, IX, X and (rarely) VI can be encountered following surgery of the cerebellopontine angle. Although cranial nerves IX and X are not by definition in the cerebellopontine angle, their function can become impaired with the resection of large tumors.

    Postoperative facial nerve paresis of various degrees can be evident immediately following surgery. Interestingly, if there is complete anatomic disruption of the nerve at the time of surgery, the patient may be able to close the eye for a period of 24 to 48 h following surgery with a subsequent progression to complete facial paralysis. More commonly, however, the patient has a variable degree of preserved eye closure and facial movement immediately postoperatively. This function also can decline between the third and the fifth postoperative days, which may be due to oedema or ischemia of the nerve. If the facial nerve paralysis is so severe that the cornea is inadequately covered, the eye should be covered with a protective shield, and artificial tears and a lubricant given every 2 to 4 h. Further therapy depends on whether the nerve is anatomically intact and whether there is adequate coverage of the cornea. If the nerve is intact but dysfunctional and the patient has adequate eye closure, the patient should be followed by recovery of the nerve. If after 12 months the facial nerve function has not returned, then a facial reanimation procedure can be planned. Various techniques and results for facial reanimation are discussed in more detail below. Poor lid coverage of the cornea in more severe cases of facial nerve paresis can be addressed with a tarsorrhaphy or with the placement of either a spring or weight in the lid. If the facial nerve is disrupted, facial reanimation is performed early.

    Fifth cranial nerve injury can follow removal of a tumor of any size. The fifth nerve function should be evaluated immediately postoperatively. If corneal sensation is diminished, the eye should be covered with a protective shield and artificial tears applied every 2 to 4 h. If corneal sensation is completely absent, the patient is at an increased risk of developing a corneal abrasion, and a tarsorrhaphy should be considered strongly.

    Dysphagia with aspiration or hoarseness due to impairment of the glossopharyngeal or vagus nerves can also occur following resection of large tumors in the cerebellopontine angle. If glossopharyngeal or vagus nerve impairment is suspected, then vocal cord and pharyngeal sensation and function should be assessed as soon after extubation as possible. A modified barium swallow with video fluoroscopy is often helpful in determining oral pharyngeal function and the patient's risk of aspiration. If there is evidence of aspiration, NGT or a feeding gastrostomy tube should be placed until there is adequate recovery of these nerves.

    Diplopia can occur after resection of large tumors. It is usually from abducens nerve paresis and the majority of patients improve spontaneously. Patching the affected eye can give some relief to the patient until the nerve function returns.

    A postoperative fever and/or headache, with or without nuchal rigidity suggests the possibility of either bacterial or aseptic meningitis. Patients with aseptic meningitis present with symptoms several weeks after surgery, usually as their steroid dose is being tapered. Evaluation of these patients should include a CT scan and immediate lumbar puncture with the CSF analyzed for cell counts, Gram stain and cultures. The glucose levels of the CSF and the serum should be measured as well. Broad-spectrum intravenous antibiotics with good gram-positive and gram-negative coverage should be started and the steroid dose increased. If the cultures are negative after 48 h. the antibiotics can be stopped and the steroids can be slowly tapered off over several weeks.

    Although postoperative epidural, subdural and intracerebellar hematomas are rare, they represent the most serious complications and if not properly diagnosed and treated, may lead to catastrophe. The diagnosis is usually not difficult in the patient who has awakened from anaesthesia and then become stuporous or comatose. During the early postoperative period, monitoring of the intracranial pressure via a subdural posterior fossa monitor may help in the early detection of a developing hematoma. If the deterioration is slow, there may be time for a CT scan: however, if the deterioration is rapid, the patient is best taken to the operating room for re-exploration.

    Hydrocephalus can occur in the early postoperative period, especially in patients with a large tumor and preoperative distortion of the fourth ventricle. The patient may become symptomatic from increased intracranial pressure or may develop a full flap at the surgical site. A CT scan can confirm the diagnosis and the patient can be treated initially with a ventriculostomy. Most patients recover spontaneously and rarely is a ventriculoperitoneal shunt required.

 
  • Several procedures have been developed to improve facial tone and motor function in patients with facial nerve paralysis. The choice of the procedure is tailored to the individual patient. The ideal treatment is intracranial end-to-end anastomosis at the time of the initial surgery. Unfortunately. most often the nerve has been attenuated or destroyed, making this impossible. The alternatives then are hypoglossal-facial, spinal accessory-facial or phrenic­facial nerve anastomosis. In cases of longstanding facial paralysis (more than 2 years) other methods must be used, which include facial dynamic or static reanimation using muscle transfers, transposition or neuromuscular pedicle grafts.

    Timing of Surgery

    The timing of surgery depends on the state of integrity of the facial nerve. If it is anatomically severed and cannot be repaired intracranially. it is better to wait 3 to 4 weeks, then readmit the patient for hypoglossal-facial nerve anastomosis. If the nerve is anatomically and physiologically preserved during surgery but is without postoperative function, the anastomosis is generally not done for at least a year, because about 90 percent of the patients seem to have adequate, although delayed functional facial nerve recovery.

    Hypoglossal-Facial Nerve Anastomosis

    This procedure is performed under general anaesthesia, with the patient supine on the operating room table and with the head turned to the contralateral side. The ear lobe is stitched up anteriorly, out of the operative field. A postauricular incision is made from half an inch above the tip of the mastoid process down in front of the sternocleidomastoid muscle, for a length of approximately 10 cm. The skin and subcutaneous tissue are opened and the fascia and platysma muscle are then divided in a longitudinal fashion. The sternocleidomastoid muscle is identified and retracted laterally. Dissection continues superiorly and medially. The cervical fascia is identified and opened. Then the posterior belly of the digastric muscle is identified and dissection is carried around it until its anteriomedial tendinous portion is identified. The hypoglossal nerve is located beneath the posterior belly of the digastric muscle. It may be identified by following the descending ansa hypoglossi up until it meets with the hypoglossal nerve.

    Attention is turned to the area of the mastoid tip. Using a periosteal elevator, the digastric muscle is partially separated from the periosteum of the mastoid process. The tip of the mastoid process is rongeured away, improving visualization of the area of the styloid process and the stylomastoid foramen. Sharp dissection for the exposure of the facial nerve at its exit from the stylomastoid foramen is done. Occasionally, the surgeon must dissect through the posterior part of the parotid gland to identify this nerve. Once both the facial and hypoglossal nerves have been identified, the hypoglossal nerve is sectioned sharply at the point where it begins to branch. The facial nerve is sectioned at the stylomastoid foramen. The proximal end of the hypoglossal nerve is swung upward and posteriorly, adjacent to the posterior belly of the digastric muscle to contact the distal end of the facial nerve. Using microsurgical technique, the two ends are anastomosed using 10-0 Prolene sutures. Care must be taken to ensure that the nerve is not angulated or under tension. After the anastomosis is complete, the wound is closed in a standard fashion. Another alternative is to section half of the hypoglossal nerve and perform anastamosing so as not to loose completely the essential function of the hypoglossal nerve.

    Spinal Accessory-Facial Nerve Anastomosis

    The incision is identical to the one used for the hypoglossal-facial nerve anastomosis. The sternocleidomastoid muscle is identified and retracted laterally and inferiorly, exposing the posterior belly of the digastric muscle, The spinal accessory nerve may be identified entering the posterior aspect of the sternocleidomastoid muscle. To expose the distal end of the facial nerve, the technique described above is used. Once the facial nerve has been divided at the stylomastoid foramen, the spinal accessory nerve is sectioned in its most distal portion, roughly where it enters the sternocleidomastoid muscle. The proximal spinal accessory nerve is swung around superiorly and posteriorly and is sutured to the distal facial nerve.

    Phrenic-Facial Nerve Anastomosis

    Two incisions are used. The first is similar to the one described for the hypoglossal-facial and the spinal accessory-facial nerve anastomoses; it is used to expose the distal facial nerve right at the stylomastoid foramen. The second incision is placed approximately two finger breadths above the clavicle in the supraclavicular fossa. The sternocleidomastoid muscle is retracted medially and superiorly, exposing the anterior scalene muscle. The phrenic nerve is in front of the anterior scalene muscle, underneath the fascia. Once the nerve is identified, it is cut at its lowermost end on the anterior scalene muscle. The proximal end of the phrenic nerve is brought up underneath the sternocleidomastoid muscle and is sutured to the cut end of the facial nerve. It is recommended that the phrenic nerve be cut and brought up first. to help judge the length of facial nerve that will be needed to perform the anastomosis without tension. If there is trouble obtaining the needed length, it is always possible to perform a mastoidectomy and expose the facial nerve higher up in the temporal bone.

    Results of Facial Nerve Anastomotic Procedures

    with a successful procedure the facial muscular tone show that with a successful procedure the facial muscular tone shows signs of recovery at 4 to 6 months, with restoration of a symmetrical face at rest. Movement of the ipsilateral side usually appears first about the oral commissure, then progresses to the cheek, lips, and orbits over the ensuing 18 months

 

 
 

 
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