Springer Nature is making SARS-CoV-2 and COVID-19 research free. View research | View latest news | Sign up for updates

Recordings from the facial nucleus in the rat: signs of abnormal facial muscle response


On the basis of results of electrophysiological studies in patients undergoing microvascular decompression (MVD) operations to relieve hemifacial spasm (HFS), we have postulated that the abnormal muscle response characteristically found in patients with HFS is the result of irritation of the facial nerve by the blood vessel that is compressing the facial nerve near its exit from the brainstem in these patients. This abnormal muscle response is seen when one branch of the facial nerve is electrically stimulated and recordings are made from muscles that are innervated by other branches of the facial nerve. We further hypothesized that the facial nucleus is hyperactive in patients with HFS and that the spasm and the abnormal muscle response are results of a phenomenon known as “kindling”. These hypotheses are supported by recent studies showing that chronic electrical stimulation of the facial nerve trunk in rats near the brainstem results in an abnormal muscle response that is similar to that seen in patients with HFS. In this paper, we present the results of recording from the facial motonucleus in rats that had been subjected to repeated electrical stimulation of the facial nerve. The results indicate that the abnormal muscle response in these rats was caused by changes in the function of the facial motonucleus. We interpret these results as showing that the physiological abnormalities that give rise to the signs of HFS in man are located in the facial motonucleus, and that the changes in the function of the nucleus are produced by chronic antidromic neural activity resulting from close contact between a blood vessel and the facial nerve.

This is a preview of subscription content, log in to check access.


  1. Auger RG, Piepgras DG, Laws ER, Miller RH (1981) Microvascular decompression of the facial nerve for hemifacial spasm: clinical and electrophysiologic observations. Neurology 31: 346–350

  2. Courville J (1966) Rubrobulbar fibers to the facial nucleus and the lateral reticular muscles (nucleus of the lateral funiculus): an experimental study in the cat with silver impregnation methods. Brain Res 1: 317–337

  3. Esteban A, Molina-Negro P (1986) Primary hemifacial spasm: a neurophysiological study. J Neurol Neurosurg Psychiat 49: 58–63

  4. Esslen E (1957) Der Spasmus facialis — eine Parabioseerscheinung. Dtsch Z Nervenh 176: 149–172

  5. Fanardjian VV, Manvelyan LR (1987) Mechanisms regulating the activity of facial nucleus motoneurons. IV. Influences from the brainstem structures. Neuroscience 20: 845–853

  6. Ferguson JH (1978) Hemifacial spasm and the facial nucleus. Ann Neurol 4: 97–103

  7. Gardner JW (1962) Concerning the mechanism of trigeminal neuralgia and hemifacial spasm. J Neurosurg 19: 947–958

  8. Goddard GV (1967) Development of epileptic seizures through brain stimulation at low intensity. Nature 214: 1020–1021

  9. Goddard GV, McIntyre DC, Leech CK (1969) A permanent change in brain function from daily electrical stimulation. Exp Neurol 25: 295–330

  10. Hopf HC, Lowitzsch K (1982) Hemifacial spasm: location of the lesion by electrophysiological means. Muscle Nerve 5: 584–588

  11. Jannetta PJ (1977) Observations on the etiology of trigeminal neuralgia, hemifacial spasm, acoustic nerve dysfunction and glossopharyngeal neuralgia: definitive microsurgical treatment and results in 117 patients. Neurochirurgia 20: 145–154

  12. Jannetta PJ, Abbasy M, Maroon JC, Morales-Ramos F, Albin MS (1977) Etiology and definitive microsurgical treatment of hemifacial spasm: operative techniques and results in forty-seven patients. J Neurosurg 47: 321–328

  13. Jannetta PJ (1981) Hemifacial spasm. In: Samii M, Jannetta PJ (eds) The cranial nerves. Springer, Heidelberg, pp 484–493

  14. Kim P, Fukushima T (1984) Observations on synkinesis in patients with hemifacial spasm. J Neurosurg 60: 821–827

  15. Kitai ST, Tanaka T, Tsukahara N, Yu H (1972) The facial nucleus of the cat: antidromic and synaptic activation and peripheral nerve representation. Brain Res 16: 161–183

  16. Kreutzberg GW, Barron KD (1978) 5′-Nucleotidase of microglial cells in the facial nucleus during axonal reaction. J Neurocytol 7: 601–610

  17. Magun R, Esslen E (1959) Electromyographic study of reinnervated muscle and of hemifacial spasm. Am J Physiol 38: 79–86

  18. Melvill-Jones G, Mandl G (1983) Neurobionomics of adaptive plasticity: integrating sensorimotor function with environmental demands. In: Desmedt JE (ed) Motor control mechanisms in health and disease. Raven Press, New York, pp 1047–1071

  19. Metson R, Nuwer M, Hanson DG, Honrubia V (1985) Facial nerve evoked potentials. Otolaryngol Head Neck Surg 93: 747–753

  20. Møller AR, Jannetta PJ (1984) On the origin of synkinesis in hemifacial spasm (HFS): results of intracranial recordings. J Neurosurg 61: 569–576

  21. Møller AR, Jannetta PJ (1985a) Hemifacial spasm: results of electrophysiologic recording during microvascular decompression operations. Neurology 35: 969–974

  22. Møller AR, Jannetta PJ (1985b) Microvascular decompression in hemifacial spasm: intraoperative electrophysiological observations. Neurosurgery 16: 612–618

  23. Møller AR, Jannetta PJ (1986a) Physiological abnormalities in hemifacial spasm studied during microvascular decompression operations. Exp Neurol 93: 584–600

  24. Møller AR, Jannetta PJ (1986b) Blink reflex in patients with hemifacial spasm: observations during microvascular decompression operations. J Neurol Sci 72: 171–182

  25. Møller AR (1987) Hemifacial spasm: ephaptic transmission or hyperexcitability of the facial motor nucleus? Exp Neurol 98: 110–119

  26. Møller AR, Jannetta PJ (1987) Monitoring facial EMG responses during microvascular decompression operations for hemifacial spasm. J Neurosurg 66: 681–685

  27. Nielsen VK (1984a) Pathophysiological aspects of hemifacial spasm. I. Evidence of ectopic excitation and ephaptic transmission. Neurology 34: 418–426

  28. Nielsen VK (1984b) Pathophysiological aspects of hemifacial spasm. II. Lateral spread of the supraorbital nerve reflex. Neurology 34: 427–431

  29. Nielsen VK, Jannetta PJ (1984) Pathophysiological aspects of hemifacial spasm. III. Effects of facial nerve decompression. Neurology 36: 891–897

  30. Sanders DB (1989) Ephaptic transmission in hemifacial spasm: a single-fiber EMG study. Muscle Nerve 12: 690–694

  31. Sen CN, Møller AR (1987) Signs of hemifacial spasm created by chronic stimulation of the facial nerve in the rat. Exp Neurol 98: 336–349

  32. Valls-Sole J, Tolosa ES (1989) Blink reflex excitability cycle in hemifacial spasm. Neurology 39: 1061–1066

  33. Wada JA (1981) Kindling 2. Raven Press, New York

  34. Wall PD (1977) The presence of ineffective synapses and the circumstances which unmask them. Philos Trans R Soc Lond B 278: 361–372

Download references

Author information

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Møller, A.R., Sen, C.N. Recordings from the facial nucleus in the rat: signs of abnormal facial muscle response. Exp Brain Res 81, 18–24 (1990).

Download citation

Key words

  • Facial motonucleus
  • Hemifacial spasm
  • Kindling
  • Animal model of hemifacial spasm
  • Rat