Hypoglossal-facial anastomosis induced central plastic changes in the blink reflex circuitry

Outcomes and complications of direct end-to-side facial-hypoglossal nerve anastomosis according to the modified May technique

OBJECT

The aim of this study was to address the efficiency and safety of direct end-to-side facial-hypoglossal nerve anastomosis for facial palsy rehabilitation.

METHODS

The authors conducted a retrospective study of 12 consecutive procedures performed between December 2000 and February 2006. Facial palsies were caused by the surgical removal of tumors in the brainstem, cerebellopontine angle, or mastoid process. Direct end-to-side facial-hypoglossal anastomosis was performed in each case. Facial function (evaluated using the overall percentage of facial function and House-Brackmann scale grades), as well as tongue trophicity and mobility, were assessed at 6, 12, and 24 months after surgery. Postoperative early and late complications were systematically reviewed.

RESULTS

The mean delay between tumoral and reparative surgery was 15.9 +/- 4 months (median 11 months). Preoperatively, the mean percentage facial function score was 11.6 +/- 1.7% (45% of patients with House-Brackmann Grade 5 facial palsy and 55% of patients with House-Brackmann Grade 6). Mean facial function scores increased to 19.3, 32.2, and 43.8% at 6, 12, and 24 months after surgery, respectively. Twenty-four months after surgery, 50% of cases had House-Brackmann Grade 3 facial palsy and 50% had Grade 4. A significantly better recovery at 24 months was observed postoperatively for neural lesions occurring in the mastoid or the brainstem compared with those in the cerebellopontine angle. Tongue hemiparesis was observed in 5 patients (41.7%), 2 of whom had tongue hypotrophy (16.7%). No patient complained of swallowing or speech disturbance. Facial synkinesis was noted in 1 patient (8.3%).

CONCLUSIONS

Facial recovery after direct end-to-side facial-hypoglossal nerve anastomosis is similar to results observed with end-to-end or end-to-side facial-hypoglossal nerve anastomosis with an interpositional graft. Tongue hypotrophy and palsy were observed in a small number of cases. This procedure allows one to minimize, although not fully prevent, facial synkinesis. The site of the neural lesion appears to be an important factor in the prognosis of recovery.

Electrodiagnostic studies of the facial nerve in peripheral facial palsy and hemifacial spasm

Electrodiagnostic (EDX) assessment is one of the most important aspects in the evaluation of the two most common disorders of the facial nerve: facial palsy and hemifacial spasm. Facial palsy is usually an acute disorder that resolves in a few weeks but, in a number of cases, leads to a postparalytic facial syndrome featuring muscle synkinesis, myokymia, and involuntary mass contractions of muscles on the affected side. Hemifacial spasm is usually a chronic disorder characterized by paroxysms of involuntary, clonic, and synchronous twitching of all facial muscles on the affected side. EDX studies provide information on lesion location and severity, pathophysiology underlying the two disorders, and differential diagnosis between syndromes presenting with abnormal facial muscle activity. This monograph is intended to describe the most relevant EDX findings in the two disorders and the most appropriate timing for the examinations in order to provide useful information for prognosis and therapeutic decision-making.

Ipsilateral facial sensory and motor responses to basal fronto-temporal cortical stimulation: Evidence suggesting direct activation of cranial nerves

To clarify the generator mechanism of sensory and motor facial responses ipsilateral to electrical stimulation of the inferior fronto-temporal cortex in epilepsy patients. Out of 30 patients who have been evaluated with chronically implanted subdural electrodes for medically intractable partial seizure or brain tumor involving the basal frontal or temporal cortex, 4 patients (age ranging 24-57 years) showed sensory and motor responses in the ipsilateral face to high frequency electrical cortical stimulation of the inferior fronto-temporal cortex. We investigated motor evoked potentials (MEPs) in the facial muscle by single pulse stimulation in 2 out of 4 patients. Three patients showed both sensory symptoms and muscle contraction in the ipsilateral lower face when the orbitofrontal or basal temporal cortex was stimulated with 50 Hz electric current. One patient had only sensory symptoms in the lower face when ipsilateral basal temporal area was stimulated. MEPs at the left orbicularis oris muscle were constantly elicited with the onset latency of 7 ms throughout the stimulus rate of 2-30 Hz in 1 patient out of 2 patients was tested. In another patient, MEP onset latency was 3.0 ms with 11 Hz stimulation. With electrical stimulation of the basal fronto-temporal cortex, the ipsilateral facial twitch might occur through either the direct activation of the facial nerve by the current spread in the middle cranial fossa or through the mechanism similar to blink reflex.

Movement disorders in patients with peripheral facial palsy

Acute unilateral facial paralysis is usually a benign neurological condition that resolves in a few weeks. However, it can also be the source of a transient or long-lasting severe motor dysfunction, featuring disorders of automatic and voluntary movement. This review is organized according to the two most easily recognizable phases in the evolution of facial paralysis: (1). Just after presentation of facial palsy, patients may exhibit an increase in their spontaneous blinking rate as well as a sustained low-level contraction of the muscles of the nonparalyzed side, occasionally leading to blepharospasm-like muscle activity. This finding may be due to an increase in the excitability of facial motoneurons and brainstem interneurons mediating trigeminofacial reflexes. (2). If axonal damage has occurred, axonal regeneration beginning at approximately 3 months after the lesion leads inevitably to clinically evident or subclinical hyperactivity of the previously paralyzed hemifacial muscles. The full-blown postparalytic facial syndrome consists of synkinesis, myokymia, and unwanted hemifacial mass contractions accompanying normal facial movements. The syndrome has probably multiple pathophysiological mechanisms, including abnormal axonal branching after aberrant axonal regeneration and enhanced facial motoneuronal excitability. Although the syndrome is relieved with local injections of botulinum toxin, fear of such uncomfortable contractions may lead the patients to avoid certain facial movements, with the implications that this behavior might have on their emotional expressions.