Course and Distribution of Facial Corticobulbar Tract Fibres in The

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J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp.69.2.262 on 1 August 2000. Downloaded from 262 J Neurol Neurosurg Psychiatry 2000;69:262–265

SHORT REPORT

Course and distribution of facial corticobulbar tract ﬁbres in the lower brain stem

S Terao, N Miura, A Takeda, A Takahashi, T Mitsuma, G Sobue

Abstract tion, concluding that the facial CBT consists of The course and distribution of the facial looping fibres that descend at least to the med- corticobulbar tract (CBT) was examined ullary level and then decussate.6 The present by correlating MRI of brain stem lesions study describes our further attempt to clarify with neurological symptoms and signs the course and distribution of the facial CBT in including central (C-FP) or peripheral a larger group of patients with lower brain stem facial paresis (P-FP) in 70 patients with infarction. localised infarction of the lower brain stem. C-FP occurred more often in pa- Patients and methods tients with lesions of the lower pons or The present study investigated 70 patients upper medulla of the ventromedial brain admitted to our department at Aichi Medical stem. Some patients with dorsolateral inf- University Hospital with acute infarction of the arcts of the upper medulla to the lower caudal portion of the brain stem between 1989 pons showed C-FP, mostly on the lesion and 1998. The patients comprised 51 men and side. P-FP on the side of the lesion was 19 women with an age range of 38 to 86 years. also seen in patients with dorsolateral Brain MRI was performed within 2 weeks of involvement of the lower pons. Patients symptom onset in all patients. For MRI, T1 with ventromedial infarction of the brain and T2 weighted images were obtained in both stem showed paresis of extremities con- the axial and coronal planes. In the present tralateral to the lesion. Specific neurologi- study, all patients had symptomatic and cal symptoms and signs such as localised infarctions in the lower brain stem. dysphagia, vertigo, nystagmus, Horner’s These were not present in patients with fatal syndrome, ipsilateral cerebellar ataxia, Division of Neurology, extensive lesion or multiple lesions of the Fourth Department of and contralateral superficial sensory im- infarct. Patients were classified into the follow- pairment were seen in patients with Internal Medicine, ing six groups according to the location and http://jnnp.bmj.com/ Aichi Medical dorsolateral infarcts of the brain stem. It distribution of ischaemic lesions as detected by University, Nagakute, is hypothesised that the facial CBT de- MRI. Group A (ventromedial involvement at Aichi 480–1195, Japan scends at the ventromedial lower pons, S Terao the lower pontine level) comprised seven men N Miura near the corticospinal tract, mainly to the and four women with an age range of 58 to 73 T Mitsuma level of the upper medulla, where the years; the lesion was on the right side in six and fibres then decussate and ascend in the the left in five. Group B (ventromedial involve- Shizuoka National dorsolateral medulla to synapse in the ment at the upper medullary level) comprised Hospital, Shizuoka, contralateral facial nucleus. five men and one woman with an age range of on September 26, 2021 by guest. Protected copyright. Japan (J Neurol Neurosurg Psychiatry 2000;69:262–265) A Takeda 40 to 70; the lesion was on the right in three Keywords: facial nerve; corticobulbar tract; brain stem; and the left in three. Group C (ventromedial Tokai Central magnetic resonance imaging involvement of the middle to lower medulla) Hospital, comprised two men and one woman with an Kakamigahara, Gifu, age range of 53 to 60; the lesion was right in Japan A Takahashi The facial nucleus in humans is located dorso- one and left in two. Group D (dorsolateral laterally in the caudal pons.12The corticobul- involvement of the middle to lower medulla) Department of bar tract fibres (CBT) that connect the motor comprised eight men with an age range of 40 to Neurology, Nagoya cortex with the facial nucleus provide strongly 83; the lesion was right in four and left in four. University School of unilateral innervation to the contralateral lower Group E (dorsolateral involvement of the Medicine, Nagoya, facial muscles and bilateral innervation to the upper medulla) comprised 20 men and six Japan 1–4 G Sobue upper facial muscles. Classic symptom locali- women with an age range of 38 to 84; the lesion sation has postulated that lesions rostral to the was right in 14 and left in 12. Group F (dorso- Correspondence to: upper mid-pons result in contralateral facial lateral involvement of the lower pons) com- Dr Shin-ichi Terao paresis of central type (C-FP), whereas ipsilat- prised nine men and seven women with an age 102949@ gk.amu.aichi-med-u.ac.jp eral facial paresis of peripheral type (P-FP) range of 40 to 86; the lesion was right in seven ensues from lesions involving the inferolateral and left in nine Attempts were made to Received 2 December 1999 part of the pons.15 We previously reported on determine the rostral and caudal levels of the and in revised form 13 March 2000 two patients in whom contralateral C-FP crossing of facial CBT fibres and to localise the Accepted 23 March 2000 resulted from ventromedial medullary infarc- descending and ascending fibres from frequen-

www.jnnp.com J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp.69.2.262 on 1 August 2000. Downloaded from Course and distribution of facial corticobulbar tract ﬁbres in the lower brain stem 263

Table 1 Facial paresis in patients with lower brain stem infarcts FREQUENCY OF MAJOR SYMPTOMS AND SIGNS IN PATIENTS WITH LOWER BRAIN STEM INFARCTS Presence of C-FP (TABLE 2) Absence lesion side opposed side Presence of P-FP of FP In the three groups with ventromedial involve- Site of infarct (%) (%) lesion side (%) (%) ment of the lower brain stem (A, B, C), hemi- Ventromedial involvement: plegia on the side opposite to the lesion was a Lower pons (n=11) 0 (0) 11 (100) 0 (0) 0 (0) common sign. None of the patients in these Upper medulla (n=6) 0 (0) 4 (67) 0 (0) 2 (33) three groups showed symptoms or signs which Middle to lower medulla (n=3) 0 (0) 0 (0) 0 (0) 3 (100) Dorsolateral involvement: were seen the patients with involvement of the Middle to lower medulla (n=8) 1 (13) 0 (0) 0 (0) 7 (87) dorsolateral part at the level of lower brain Upper medulla (n=26) 9 (35) 1 (4) 0 (0) 16 (61) stem. Two patients (18%) of group A and two Lower pons (n=16) 3 (19) 0 (0) 11 (69) 2 (12) (33%) of group B had deep sensory impair- C-FP=central facial paresis; P-FP=peripheral facial paresis; FP=facial paresis. ment of the limbs and trunk on the opposite side. Table 2 Frequency of major symptoms and signs in patients with lower brain stem infarcts In the remaining three groups with dorsola- group A group B group C group D group E group F teral involvement of the lower brain stem (D, E, (n=11) (n=6) (n=3) (n=8) (n=26) (n=16) F), contralateral limb paresis occurred in only Symptom and signs (%) (%) (%) (%) (%) (%) three patients (12%) belonging to group E. In Symptoms: patients with these dorsolateral infarcts, a wide Dysphagia 0 (0) 0 (0) 0 (0) 4 (50) 14 (54) 7 (44) Vertigo 0 (0) 0 (0) 0 (0) 4 (50) 18 (69) 7 (44) variety of symptoms and signs of involvement Hiccups 0 (0) 0 (0) 0 (0) 2 (25) 6 (23) 1 (6) such as dysphagia, vertigo, hiccups, hoarse- Hoarseness 0 (0) 0 (0) 0 (0) 5 (63) 12 (46) 4 (25) ness, nystagmus, paralysis of the soft palate, Signs: Nystagmus 0 (0) 0 (0) 0 (0) 8 (100) 20 (77) 12 (75) Horner’s syndrome, facial sensory impairment, Soft palate paresis 0 (0) 0 (0) 0 (0) 6 (75) 18 (69) 0 (0) ipsilateral cerebellar ataxia, and contralateral Horner’s syndrome 0 (0) 0 (0) 0 (0) 6 (75) 19 (73) 7 (44) superficial sensory impairment of limb and Sensory impairment of face 0 (0) 0 (0) 0 (0) 7 (88) 15 (58) 9 (56) Ipsilateral cerebellar ataxia 0 (0) 0 (0) 0 (0) 7 (88) 22 (85) 11 (69) trunk were present. Contralateral limb and truncal superficial sensory Discussion impairment 0 (0) 0 (0) 0 (0) 8 (100) 19 (73) 8 (50) Contralateral limb and Some CBT fibres in humans are thought to truncal deep sensory leave the corticospinal tract (CST) in the brain impairment 2 (18) 2 (33) 0 (0) 0 (0) 0 (0) 0 (0) stem,7–11 with a portion of them descending in Contralateral limb paresis 11 (100) 6 (100) 3 (100) 0 (0) 3 (12) 0 (0) the medial lemniscus as an aberrant pyramidal tract, although their precise topographic anat- cies of occurrence of C-FP or P-FP and other omy is not clear.3710 To explain C-FP from brain stem signs. Furthermore, to elucidate the lesions caudal to the facial nucleus, damage to course and location of facial CBT in axial sec- the aberrant pyramidal tract has been postu- tions of the brain stem, a comparative analysis lated, including involvement of the classic was conducted of major neurological symp- Pick’s bundle,12–15 which reverses course in the toms and signs among the six groups. pyramidal decussation and ascends in the CST to connect with the motor nuclei of some cra- Results nial nerves. However, whether or not the facial

FREQUENCY OF OCCURRENCE OF C-FP AND P-FP nucleus actually receives such CBT fibres has http://jnnp.bmj.com/ (TABLE 1) not been determined.31617 A C-FP occurred in 29 of the total 70 patients. Currier18 has hypothesised that facial CBT The C-FP seen in these patients was relatively fibres leave the pyramidal tract at the pon- mild, and recovery was almost complete within tomedullary junction and descend caudally to 1 to 2 months of onset. All 11 patients of group at least the middle medullary levels before most A (ventromedial involvement of lower pons) of them cross to the opposite facial nucleus. showed C-FP on the side opposite to the Interruption of these fibres by infarction at a

lesion. Among the six patients of group B (ven- predecussation level has been postulated to on September 26, 2021 by guest. Protected copyright. tromedial involvement of upper medulla), four result in a contralateral C-FP. Cavazos et al19 patients (67%) showed C-FP on the side have described some fibres of the facial CBT as opposite to the lesion. The remaining two descending ipsilaterally, making a loop as cau- patients (33%) showed no evidence of C-FP.In dally as the upper medulla before decussating group C (ventromedial involvement at the and ascending to the contralateral facial middle to lower medulla), C-FP was not nucleus. Our results indicate that C-FP oc- present in any of the three patients. curred more often in patients with a lesion Of the eight patients in group D (dorsola- extending from the lower pons to the upper teral involvement of the middle to lower medulla than in those with a lesion in the mid- medulla), only one (13%) developed C-FP on dle to lower medulla, regardless of whether the the side of the lesion. A C-FP was also clinically lesion was located ventromedially or dorsola- present in 10 of the 26 patients in group E terally. Kim et al20 have also reported that, in (dorsolateral involvement of the upper me- patients with lateral medullary infarction, dulla), and C-FP of the nine patients (35%) C-FP was seen more often with high than mid- was on the side of the lesion and one patient dle to low medullary lesions. (4%) on the opposite side. Of the 16 patients in Our present findings suggest that the facial group F (dorsolateral involvement of the lower CBT descends at least to the level of the upper pons), P-FP occurred on the side of the lesion medulla, where the fibres cross the midline, even in 11 patients (69%), and C-FP in another though their specific topographic anatomy may three (19%). vary from one person to another (figure A). The

www.jnnp.com J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp.69.2.262 on 1 August 2000. Downloaded from 264 Terao, Miura, Takeda,et al

A CBT CST Midbrain

Bilateral for upper face Pons

Facial nucleus

F A

E Crossed for B lower face Medulla

1 Corticospinal tract B Ventral 4 2 Medial lemniscus 3 Medial longitudinal fasciculus 1 4 Hypoglossal nerve (XII) dc 6 5 Hypoglossal nucleus 2 6 Inferior olivary nucleus 7 Spinothalamic tract 8 Nucleus ambiguus 7 9 Solitary nucleus 10 11 http://jnnp.bmj.com/ 8 10 Descending sympathetic tract as 3 12 11 Vagus nerve (X) 9 13 12 Spinal tract and nucleus 5 15 14 of trigeminal nerve (V) 13 Inferior cerebellar peduncle

Dorsal 14 Vestibular nucleus 15 Dorsal nucleus of vagus on September 26, 2021 by guest. Protected copyright. (A) Schematic diagram of pathways of the facial corticobulbar tract (CBT). The corticospinal tract is designated CST.The six grey areas show the locations of lower brain stem infarctions in the groups studied, A to F.(B) Facial corticobulbar tract (CBT) fibre distribution is shown in the upper medulla: dc=descending fibres; as=ascending fibres. facial CBT, then, could be represented as loop- ascend in the dorsolateral medulla to connect ing fibres, most of which decussate in the upper with the facial nucleus (figure A and B). On the medulla. This schema is an alternative to placing other hand, as C-FP resulting from involvement these CBT fibres in the aberrant pyramidal of ascending pathways occurred less often than tract, which reverses course in the lower medulla C-FP from involvement of descending path- to ascend from the pyramidal decussation. Jenny ways; these ascending pathways may be widely 4 et al have reported that descending CBT fibres dispersed in the dorsolateral medulla rather than innervated the lower facial motor nuclear region representing a discrete bundle. bilaterally in the monkey, although with contral- Additional clinicoradiological, clinicopatho- ateral predominance. Therefore, non- logical, and neuroanatomical studies should decussating CBT fibres supplying the ipsilateral help to further clarify the courses of central lower facial nucleus may be present in pathways, including the CBT, in humans. humans.421 On the basis of locations of facial CBT seen in axial sections, we would argue that these CBT fibres descend near the CST, mostly This work was supported by a research grant for longevity to the upper medulla, where they decussate and sciences (110-05) from the Ministry of Health and Welfare.

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