© 1991 S. Kargcr A G , Basel 0 0 14-302 2/91/0313-015 2$ 2.7 5/0 Eur Neurol 1991;31:152-155 Two Mesencephalic Lacunar Infarcts Presenting as Claude’s Syndrome and Pure Motor Hemiparesis Bertrand Gaymard, Denis Saudeau, Bertrand de Toffol, Pierre Larmande, Alain Autret Department of Neurology, C.H.U. Bretonneau, Tours, France Key Words. Claude’s syndrome • Pure motor hemiparesis • Lacunar infarct • Mesencephalon Introduction A special issue of this journal was recently assigned to lacunar infarcts [1], We report here two limited small infarcts of the mesencephalon located in the anterior vascular territory: one of them was restricted to the red nucleus, the other one involved selectively the pyramidal tract in the cerebral peduncle. In both cases, CT exami­ nation clearly revealed the lesion. Such locations of infarction have been reported as being exceptional. Case Report Case 1. A 53-year-old man awakened with horizontal diplopia, diz­ ziness and weakness of the right limbs. He had no important past illnesses, especially no hypertension or diabetes mellitus. There had been no prodromal phenomena. He was alert and well oriented, and his blood pressure was normal. Examination showed a full left thirdnerve paralysis with a complete ptosis of the upper lid and a d ic ­ tated fixed pupil (4 mm). There was a slight weakness in the right side and right plantar response was extensor. Sensory examination of all modalities was normal, including position sense. The initial findings of CT scan were normal. Three days after admission, the neurological examination was modified: the right motor weakness had completely disappeared, and it was therefore possible to dem­ onstrate a clear hypermetria of the right arm on the fmger-to-nose testing, a positive Stewart-Holmes sign and an ataxia of gait. Electroencephalogram (EEG) was normal, and ultrasound Doppler examination of the cervical arteries did not reveal signifi­ cant abnormalities. A second CT scan was performed 7 days after onset and showed a small lacune in the left paramedian tegmentum of the mesencephalon, corresponding to the red nucleus (fig. 1). Three months later, only a slight limitation of vertical and abduc­ tion left eye movements was still present. Case 2. A 72-year-old right-handed woman was admitted be­ cause of left hemiplegia. She had no medical history except for a recently discovered atrial fibrillation. The day before admission, she woke up with a severe weakness of the left leg. Examination revealed a good orientation in time and space, no abnormalities of speech and comprehension, and a normal blood pressure (130/80). She had a motor deficit on the left side graded 0/5 in the lower limb and 2/5 in the upper limb. The face was almost spared, with only a very slight facial asymmetry. She was not dysarthritic. Tendon reflexes were brisk on the left side with a Babinski sign. Sensitivity to pin­ prick on both sides was intact, vibration and position sense were normal. There was a moderate miosis on the right side (right pupil: 2 mm, left pupil: 4 mm), more marked in dim illumination. A ptosis of the upper lid and an upside-down ptosis of the lower lid was noticed on the same side. There was no heterochromia of the iris. Visual acuity and visual fields were normal. Eye movements, recorded by direct-current electro-oculography, showed normal hor­ izontal saccades and pursuit movements. EEG, brainstem auditory and cortical somatosensory evoked potentials were completely nor­ mal. An atrial fibrillation was present on electrocardiogram. A CT scan performed 2 days after admission showed a small hypodense area consistent with a lacunar infarct located in the external 2/3 of the foot of the right cerebral peduncle (fig. 2). No other abnormalities were noticed, especially in the hemisphere. Echotomography and ultrasound Doppler examination of the inter­ nal carotid and vertebral arteries were normal. One month after stroke, only a slight weakness of the left leg persisted, and the patient could walk by herself. Downloaded by: Kings's College London 137.73.144.138 - 11/2/2017 10:49:11 PM Abstract. Two exceptional cases of mesencephalic lacunar infarcts located both in the anterior vascular territory are reported. In patient 1, the infarct selectively involved the red nucleus, thus resulting in a Claude’s syndrome. In patient 2, the lesion was limited to the external 2/3 of the cerebral peduncle, and was responsible for a pure motor hemiplegia (PMH). CT scan easily demonstrated the lesion in both cases. Claude’s syndrome is very unusual, and PMH has only been reported once before in a mesencephalic infarct. The reasons why these lesions are so uncommon are discussed. Fig. 1. CT scan of patient 1. Hypodense lesion in the area of the left red nucleus (on the right side on the scan). Discussion We have described 2 patients with small infarcts of the mesencephalon. The clinical feature of the first pa­ tient is consistent with Claude’s syndrome: complete ipsilateral third-nerve paralysis and contralateral cere­ bellar syndrome. Topographical diagnosis is here univocal, since the oculomotor nerve and the superior cerebel­ lar peduncle (after its decussation) only meet at the level of the red nucleus. Since Claude’s initial report in 1924 [2], this syndrome has only been reported in 3 ischemic lesions [3-5]. In the two recent reports [4, 5], a hypodense lesion limited to the red nucleus was only visible in one case [5]. Duvemoy [6] has recently studied in detail the vascu­ larization of the brainstem in man. According to his findings, the vascularization of the mesencephalon can be divided into 3 groups: anterior, lateral and posterior groups. Only the anterior group was concerned in our 2 patients and will be considered here. This group is divided in an anterolateral group formed by small branches arising from several medium-sized arteries (collicular, posteromedial-choroidal, antero-choroidal and posterior cerebral arteries), supplying the pyramidal tract, and in an anteromedial group, or peduncular arter­ 153 Fig. 2. CT scan of patient 2. Hypodensity in the external 2/3 of the right cerebral peduncle (on the left side on the scan). ies, divided into 4 subgroups, inferior and superior, median and lateral (fig. 3). The arteries of these 4 subgroups are small but nu­ merous, display superficial anastomoses, and variations in their course and territory are more numerous than usually thought [6, 7], Furthermore, the superior and the inferior subgroups of these arteries supply territories outside the mesencephlon, namely the thalamus and the pontine tegmentum. The median subgroup supplies the nuclei of the third and fourth cranial nerves, and the lateral subgroup is the main supply of the red nucleus [6], Therefore, the characteristics of the vascularization of the anterior mesencephalon (anastomoses, variations in territories, extent to the thalamus and the pons) explain why the clinical features of infarcts in this region are so numerous, and why the selective involvement of the red nucleus is so exceptional. In the second case, the clinical examination is consis­ tent with a pure motor hemiparesis (PMH) as it was ini­ tially described by Fischer and Curry in 1964 [8]: hemi­ paresis without associated sensory deficit, aphasia, hom­ onymous hemianopia or higher cortical-function deficit. This well-defined clinical syndrome is the most frequent lacunar syndrome, and typically results from a lacunar infarct in the posterior limb of the contralateral internal Downloaded by: Kings's College London 137.73.144.138 - 11/2/2017 10:49:11 PM Claude’s Syndrome and Pure Motor Hemiparesis Gaymard/Saudeau/dc Toffol/Larmande/Autret 154 Medial lemniscus Red nucleus Corticospinal tract Posteromedial choroidal artery Posterior cerebral artery Oculomotor nerve Basilar artery Fig. 3. Vascularization of the pyramidal tract. Internal capsule (a), mesencephalon (b), pons (c). me­ dulla oblongata (d). b-d Spotted area represents the anterolateral vascular territory: the anteromedial vascular territory is figured between the midline and the dotted line (re­ drawn from [16]). capsule, but lesions in the basis pontis are not rare [9- exactly fits the topographical distribution of the fibers of 11] . Since the advent of CT, several other etiologies have the pyramidal tract in the cerebral peduncle [15]. We been described: demyelinating disease, brain abcess, believe that the exceptional occurrence of infarctions in brain tumor, intracranial or subdural hematoma [11, the pyramidal tract at the level of the cerebral peduncle 12] . Theoretically, PMH could result from any lesion may be partly explained by the observation of its vascu­ able to involve the pyramidal tract selectively: in the larization (fig. 3). In the internal capsule, it is vascular­ medullary pyramid, the pons, the cerebral peduncle or in ized by small penetrating branches directly arising from the internal capsule. However, in this syndrome, the the middle cerebral artery, thus being fully exposed to great frequency of capsular and pontine lesions differs the pathological consequences of hypertension. The dramatically from the exceptional occurrence of bulbar same configuration exists in the pons, where the corti­ and peduncular lesions. cospinal tract is vascularized by thin vessels belonging to Indeed, an isolated medullary pyramid infarct is very the anteromedial group of arteries. These small arteries rare [ 13], and to our knowledge, PMH resulting from a form a 90° angle with the basilar artery (2-3 mm diam­ peduncular infarct has only been reported once before, eter) from which they directly arise [6], On the contrary, by Ho in 1982 [14]. In our case, it should be noted that because of the more lateral position of the corticospinal the distribution of the motor deficit (leg 0/5, arm 2/5, tract in the upper mesencephalon, its vascularization face spared) and the absence of oculomotor abnormali­ here depends on the anterolateral group, formed by ties suggest that the corticonuclear tract was spared, and small arteries distant from the basilar artery, arising Downloaded by: Kings's College London 137.73.144.138 - 11/2/2017 10:49:11 PM Collicular artery 155 Claude’s Syndrome and Pure Motor Hemiparesis from medium-sized arteries (1-2 mm diameter): collicular, superior cerebellar, and posteriomedial-choroidal ar­ teries (see supra), with which they form a more acute angle, thus providing more loss of energy in blood flow [17]. A similar configuration is found in the medulla oblongata where the bulbar pyramids, although medially situated, are vascularized by inclinated (downward) pen­ etrating arteries arising from the anterospinal artery, a mediumsized artery arising from the vertebral artery. Furthermore, in the anterolateral region of the mesen­ cephalon, the carotid and vertebrobasilar systems are intermiggled, thus providing an additional protection against ischemia [17]. The occurrence of a Homer’s syndrome has never been described before in a limited lesion of the mesen­ cephalon. There were no ultrasound abnormalities on the internal carotid artery, and two consecutive CT scans did not show any other abnormalities than the right mesencephalic infarct. Although several locations for this syndrome are possible [ 18-20], it can be suggested that it was secondary to a lesion on the first neuron of the oculosympathic pathway. The descending sympathie tract arises from the poste­ rolateral region of the hypothalamus, and is largely un­ crossed [20]. Then, its trajectory probably occupies a lat­ eral position in the brainstem, but its precise location is still unknown, especially in the mesencephalon [20], The anterior region of the upper mesencephalon is just cau­ dal to the hypothalamus; thus, in the present case, the sympathie tract could have been affected just after and under its emergence from the hypothalamus. The two small infacts we have described here oc­ curred in 2 patients with normal blood pressure and nor­ mal Doppler examination; one of them had an atrial fibrillation. Therefore, their etiology could be a cardiac embolism or a local arterial microembolism. 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