Magnetic resonance imaging of medial medullary infarction

Medial medullary infarction is characterized by ipsilateral hypoglossal nerve palsy, contralateral hemiparesis sparing the face, and contralateral disturbance of deep sensation. Although it is possible to make a clinical diagnosis in typical patients, diagnosis is difficult if hypoglossal nerve palsy is absent. We describe a patient with medial medullary infarction without hypoglossal nerve palsy. The patient suffered from left hemiplegia and homolateral disturbance of deep sensation. Magnetic resonance imaging revealed the site of the lesion to be in the medial portion of the upper medulla oblongata. The result of somatosensory evoked potential testing was compatible with disturbance of the medullary medial lemniscus. In a review of the literature, we examined the relation between clinical features and lesion location in 16 patients with medial medullary infarction and compared these to the present patient. Motor paresis was present in every patient, while disturbance of deep sensation was recorded in nine of 13 patients and hypoglossal nerve palsy in six of 14 patients. In atypical patients with medial medullary infarction (such as the present patient), magnetic resonance imaging is necessary to detect the lesion and to make a clinical diagnosis.     

Medial medullary infarction demonstrated by MRI

A 67-year-old woman with medial medullary infarction is reported, including clinical manifestations, MRI and angiographical findings, and results of evoked potentials. She suffered from contralateral hemiplegia and disturbance of deep sensation. Motor paresis of the tongue was absent. Magnetic resonance imaging revealed a lesion in the medial portion of the medulla oblongata. The 17 cases previously reported with medial medullary infarction are reviewed. Only 3 cases had triad of medial medullary infarction, contralateral hemiparesis, deep sensory disturbance, and ipsilateral hypoglossal paresis. Therefore, lesion detection is necessary to diagnose medial medullary infarction. Most infarctions limited to the upper third of the medulla were caused by occlusions of vertebral arteries or their branches and prognosis was good. In contrast, infarctions in the lower two thirds were caused by occlusions of anterior spinal arteries and their branches and the prognosis was poor. Thus localization of the lesion using MRI plays an important role to predict the prognosis.     

The medullary vascular syndromes revisited

There are two major vascular syndromes of the medulla oblongata: the medial and the lateral. The medial medullary syndrome is characterized by the triad of ipsilateral hypoglossal nerve palsy with contralateral hemiparesis and loss of deep sensation. Lateral medullary infarction commonly presents with Homer's syndrome, ataxia, alternating thermoanalgesia, nystagmus, vertigo and hoarseness. Combinations of the two major syndromes occur as bilateral medial medullary, hemi-medullary and bilateral lateral medullary syndromes. Each of these syndromes frequently manifests with incomplete or atypical findings depending on the extent of the lesion. Magnetic resonance imaging has been useful in the clinical diagnosis of medullary infarctions. The site of the lesion may help predict the arteries involved.     

Sensory dermatomal representation in the medial lemniscus

BACKGROUND: Restricted sensory deficits along the somatotopic topography of the medial lemniscus rarely develop in medial medullary infarction. We describe a patient with medial medullary infarction who presented with dermatomal sensory deficits caused by a medial lemniscal lesion. CASE DESCRIPTION: A 58-year-old man presented with sudden right-sided hemiparesis and paresthesia. He had noticed the paresthesia below the level of the right L5 dermatome, where his vibration and position senses were mildly diminished. His paresthesia was more severe over the right calf and foot. Magnetic resonance images of the brain showed an acute small infarct in the medial-ventral portion of the left rostral medulla oblongata. A nerve conduction study and electromyography showed no abnormalities. At follow-up, the patient's motor and sensory deficits had improved considerably. CONCLUSIONS: The patient showed lemniscal sensory deficits below the right L5 dermatome that were caused by the partial involvement of the medial lemniscus. These findings suggest that lemniscal sensory dermatomal representation is preserved at least up to the level of the medulla oblongata.     

Diffusion-weighted magnetic resonance imaging (MRI) in acute brain stem infarction]

Diffusion-weighted magnetic resonance imaging (DWI) provides one of the earliest demonstrations of ischemic lesions. However, some lesions may be missed in the acute stage due to technical limitation of DWI. We therefore conducted the study to clarify the sensitivity of DWI to acute brain stem infarctions. Twenty-eight patients with the final diagnosis of brain stem infarction(midbrain 2, pons 9, medulla oblongata 17) who had been examined by DWI within 24 hours of onset were retrospectively analyzed for how sensitively the initial DWI demonstrated the final ischemic lesion. Only obvious(distinguishable with DWI alone without referring clinical symptoms and other informations) hyperintensity on DWI was regarded to show an ischemic lesion. Sixteen(57.1%) out of 28 patients had brain stem infarctions demonstrated by initial DWI. In the remaining 12 cases, no obvious ischemic lesion was evident on initial DWI. Subsequent MRI studies obtained 127 hours, on average after the onset showed infarction in the medulla oblongata in 11 cases and in the pons in one case. Negative findings of DWI in the acute stage does not exclude possibility of the brain stem infarction, in particulary medulla oblongata infarction.     

Diagnosis of acute cerebral infarction using diffusion-weighted imaging by low field (0.2 T) magnetic resonance image]

The purpose of this study is to confirm the diagnosis of acute cerebral infarction on diffusion-weighted imaging using low field (0.2 T) magnetic resonance image(MRI). Acute cerebral infarctions in 51 patients were examined on diffusion-weighted imaging using low field MRI within 48 hours after clinical symptoms. Diffusion-weighted imaging was examined using line scan method. Twenty-four cases were cortical infarction, and twenty-two cases were perforating infarction. In five cases out of 51 cases, ischemic regions were not detected as abnormal high signal intensity area on diffusion-weighted imaging. Four cases of no abnormal detection were transient ischemic attack, and the other one was a perforating infarction. The earliest detection time in cortical infarction cases was 1 hour and 20 minutes. On the other hand, the earliest detection time in perforating infarction cases was 3 hours. Detective ability for acute cerebral infarction on diffusion-weighted imaging by low field MRI was depending on both size and lesion of infarction. That is to say, either small size or brain stem infarction was hard to detect. Thin slice and vertical slice examination for the infarction may improve to diagnose in low field MRI. Our conclusion is acute cerebral infarction was able to be diagnosed on diffusion-weighted imaging by low field as well as high field MRI.     

Bilateral medial medullary infarction

We present a case of bilateral medial medullary infarction demonstrated by magnetic resonance imaging (MRI) and review 12 previously reported cases. We classify these 13 cases (including the present case) into two groups according to the extent of the ischemic region: type 1, the ischemic lesion developed from the medullary pyramid to the medial longitudinal fasciculus; type 2, the lesion was confined to the medullary pyramid.A 71 year old man presented with slight disturbance of consciousness, dysarthria, disturbance of leftward gaze, no gag reflex and tetraparesis. He developed nearly complete horizontal ophthalmoplegia. MRI revealed upper medial medullary infarction bilaterally that extended to the pontomedullary junction. We propose that the prognosis of type 2 bilateral medial medullary infarction is better than that of type 1. Furthermore, the prognosis of bilateral medial medullary infarction itself may be better than previously indicated.     

Life-threatening orthostatic hypotension in a case with bulbo-myelo-radiculo-neuropathy.

A 59-year-old female developed acute autonomic failure accompanied by life-threatening orthostatic hypotension. Reduced plasma noradrenaline levels and enhanced pressure response to noradrenaline infusion were compatible with a diagnosis of acute pan-dysautonomia. However, nerve conduction tests clearly revealed motor and sensory nerve involvement and abnormal F-responses. A sural nerve biopsy and catecholamine fluorescence study of the rectal mucosa revealed relatively preserved postganglionic unmyelinated nerve fibers. Six weeks later, the patient developed another episode of bulbar palsy and right hemiparesis; the MRI showed lesions in the medulla oblongata and right cervical spinal cord. The prognosis of acute pan-dysautonomia is usually unsatisfactory, but the present patient showed good steroid-responsiveness probably because impaired preganglionic sympathetic myelinated fibers and medulla oblongata recovered quickly.     

延髓梗死的临床与神经影像学分析(附73例报告)

目的探讨延髓梗死的临床与神经影像学特点。方法回顾性分析73例延髓梗死患者的临床资料和影像学检查结果。结果本组男性53例,女性20例。首发临床表现复杂多样,其中浅感觉障碍41例,眩晕39例,饮水呛咳36例,恶心呕吐32例,吞咽困难31例,构音障碍29例。梗死病灶位于延髓上段27例,中段29例,下段12例,同时累及上段和中段3例,中段和下段2例。病灶位于背外侧61例,腹内侧10例,背内侧2例。表现为经典的延髓综合征共15例,包括Wallenberg综合征12例,Dejerine综合征1例,Avellis综合征1例,Babinski-Nageotte综合征1例。结论延髓梗死常见临床表现是浅感觉障碍和后循环缺血症状,经典延髓综合征少见;延髓梗死以中上段最常见,主要发生于背外侧;头部MRI对延髓梗死的诊断有极其重要的意义。     

Bilateral medial medullary infarction presented with monoplegia of the lower limb, followed by paraplegia and finally by tetraplegia]

A 69-year-old Japanese man suddenly developed monoplegia of left lower extremity, followed by paraplegia and finally by tetraplegia. MRI revealed an infarction in bilateral medial medulla extending from the cervicomedullary junction up to the upper limit of the medulla. Both hypoglossal nerve palsy and sensory disturbance were absent. At the pyramidal decussation, fibers to the lower extremities cross caudal to the fibers going to the upper extremities, therefore right below the decussation, fibers to the lower extremities run medial side of the fibers to the upper extremities, but later the former run lateral side of the latter. In this patient, the authors considered that the lesion initially damaged the pyramidal decussation at a slightly lower level, involving the tract to left lower extremity, and then extended to right lower extremity, to the left upper extremity, finally to the right upper extremity. Bilateral medial medullary infarction must be considered in the clinical course seen as in this patient.     

Serial T2 short inversion time inversion recovery images in a patient with medullary hemorrhage]

A 52-year-old man was admitted to our hospital because of hypesthesia on the right side of his body. He had no medical history. On admission, he exhibited hypesthesia and disturbance of the touch and the vibratory sense on the right side of his body excluding the face. A brain T2* -weighted image revealed the a dot like lesion surrounded by an iso-signal lesion in the medial medulla oblongata. Therefore a diagnosis of medullary hemorrhage was made. Although a vascular malformation was considered as the cause of the hemorrhage, cerebral angiography did not reveal any vascular malformations. After admission, he developed left hypoglossal nerve palsy on day 6, and intractable hiccups on day 11. A T2* -weighted image and a FLAIR image disclosed edema surrounding the hematoma in the medial medullary lesion. T2* weighted images are useful for diagnosing and evaluating serial changes of medullary hemorrhage.     

Pure Sensory Deficit at the T4 Sensory Level as an Isolated Manifestation of Lateral Medullary Infarction

In rare cases restricted sensory deficits along the somatotopic topography of the spinothalamic tract can develop from a lateral medullary infarction. To our knowledge, isolated dermatomal sensory deficit as a single manifestation of a lateral medullary infarction has not been reported previously. A 58-year-old man presenting with sudden left-sided paresthesia complained of sensory deficit of pain and temperature below the left T4 sensory level without other neurologic deficits. Diffuse- and T2-weighted magnetic resonance imaging (MRI) of the brain showed high signal intensities in the right lower medulla oblongata, whereas thoracic-spine MRI and somatosensory evoked potentials produced normal findings.     

脑干梗塞急性期弥散MRI的探讨

目的:弥散加权MRI(DW1)因能够在早期、快速、敏感地反映出脑部缺血性病变而成为脑梗塞患者急性期诊断不可缺少的重要的检查方法,但是对于某些部位的某些小的病灶在急性期DW1有时亦不能查出。本研究以脑干梗塞的患者为对象,对急性期DW1的敏感度进一步探讨。方法:以发病24小时以内施行DWI检查的28例患者作为对象;DWI是在1.5Tesl的MR装置下,采用断层回波成像的,与此同时,还进行了T2加权MRI及水抑制成像FLAIR(fluidattenuated inversion recovery)的检查,最终梗塞灶根据平均127小时后的以上所述的MRI检查中的所见及临床症状来综合判断的,只把明确的高信号区域判断为病灶。结果:最终梗塞灶为中脑2例,桥脑9例,延髓17例。通过第一次DWI,检查出病灶的16例(敏感度57.1％),没有明确检查出病灶的12例,其中在这12例患者中有11例是在以后的MRI检查中发现为延髓病变,有1例确认为桥脑病变。从发病开始到施行DWI检查为止,时间越短,病变越不容易查出。结论:应该注意在急性期的DWI中即使没有明确的病灶,也不能否认脑干梗塞,特别是延髓梗塞。     

MRI characteristics of acute and subacute brainstem and thalamic infarctions: value of T2- and diffusion-weighted sequences

MRI including diffusion-weighted sequences (DW-MRI) has demonstrated its high sensitivity for acute supratentorial ischemic lesions. In this study we examined the sensitivity of different MRI sequences for the detection of acute brainstem and isolated thalamic infarctions. Diffusion- and T2-weighted MRI of 45 consecutive patients with signs and symptoms of infratentorial and thalamic infarction between 6/1997 and 1/2000 were analysed. The time between the onset of symptoms and the first MRI varied between 2 hours to 7 days with a median of 2 days. MRI repeats were performed in 4 patients in whom the clinical brainstem infarction had not been detected initially. Lesion detectability and size were evaluated for different brainstem and thalamic localizations. An acute brainstem or thalamic infarction as defined by the clinical condition could be identified in all patients by comparison of DW-MRI and T2-weighted images. Pons infarctions were the largest, followed by midbrain and thalamic lesions. Medulla oblongata infarctions were small in comparison. Pons, midbrain and thalamic infarctions were reliably identified beginning 12 hours after the onset of symptoms. In contrast, detectability of medulla oblongata infarctions varied within the first 24 hours and their overall visibility was worse than that of other brainstem infarctions corresponding to their small size. However, regardless of location, none of the 3 infarctions examined within the first 5 hours after the onset of symptoms could be identified. These lesions were demonstrated in follow-up examinations. In conclusion, pontine, midbrain and thalamic infarctions can reliably be visualized by a combination of DW-MRI and T2-weighted images beginning 12 hours after the ischemic attack. However, sensitivity seems to be lower earlier than 12 hours after ischemia and for medulla oblongata lesions. Received: 16 March 2001, Received in revised form: 25 April 2001, Accepted: 26 April 2001     

An autopsied case of medullary glioma with an abrupt onset of headache and hemiparesis]

We describe an 89-year-old woman who presented with an abrupt onset of headache and right hemiparesis. With the initial diagnosis of cerebral infarction, we started therapy using sodium ozagrel. The right hemiparesis worsened, however, and a continuous intravenous heparin injection showed no effect. Furthermore, nystagmus in the bilateral eyes, dysphagia, left hemiparesis, and central ventilation disorder appeared one after another in three weeks. A magnetic resonance images (MRI) of the head, performed on the fifth hospital day with regular intervals of axial sections, disclosed no lesion responsible for right hemiparesis. MRI of the brainstem and upper cervical cord, performed after two weeks with smaller intervals of axial sections, revealed a T2 high signal lesion in the left side of the medulla oblongata and upper cervical cord. After about five weeks from the onset of the disease, she died of pneumonia. With the pathological examination, we diagnosed as glioma originated in the left ventral part of medulla oblongata. Five similar cases of brainstem glioma have been reported so far. Our patient, the oldest one, showed an exceptionally rapid clinical course, instructing us to consider the possibility of medullary glioma even in the elderly patients presenting with acute onset hemiparesis followed by rapid and progressive appearance of brainstem signs.     

Transient lesion in the splenium of the corpus callosum in acute cerebellitis

We report the reversible magnetic resonance imaging (MRI) findings in a 2-year-old girl with acute cerebellitis. The high signal intensity in the cerebellum was obvious on diffusion-weighted images, and the splenium of the corpus callosum also showed high signal intensity on T2-weighted images and on diffusion-weighted images. The lesion in the splenium quickly returned to normal 72 hours later, whereas the hyperintensity in the cerebellum persisted for 1 week until clinical improvement was achieved. The findings in our patient suggested the particular vulnerability of the splenium of the corpus callosum compared to other regions and the importance of the MRI examinations including diffusion-weighted images in the early stage of encephalitis.     

A case of medial medullary infarction with persistent primitive hypoglossal artery]

A 66-year-old woman was admitted to our hospital because of vomiting, dizziness and vertigo. Neurological examination on admission revealed only upbeat nystagmus without cranial nerve symptoms, paresis, cerebellar signs or sensory disturbances. Magnetic resonance(MR) images demonstrated a new T 2 high intensity and T 1 iso-intensity signal lesion in the right upper medial medulla. This medial medullary infarction caused central vestibular dysfunction. MR angiography and digital subtraction angiography demonstrated a persistent primitive hypoglossal artery (PPHA) originating from the right internal carotid artery to the vertebrobasilar artery associated with the stenosis of the right internal carotid artery at the level of the cervical bifurcation. This is the first report of medullary infarction with persistent carotid-basilar anastomosis. We suspected this medullary infarction was caused by artery to artery embolism in the branch of the right vertebral artery through the PPHA distal originated from the stenosis of the right internal carotid artery.     

Apnea associated with Chiari malformation: medullary hemorrhage revealed by MRI

Medullary hemorrhage in the medulla oblongata of an infant with Chiari malformation, hydrocephalus, meningomyelocele and hypogenesis of the corpus callosum is reported. Four days after placement of a ventriculoperitoneal shunt, spontaneous respiration diminished. Magnetic resonance imaging (MRI) successfully revealed a small medullary hemorrhage.     

Neurogenic pulmonary edema induced by primary medullary hemorrhage: a case report

We report a case of neurogenic pulmonary edema occurring in association with primary medullary hemorrhage. A pervious healthy 28-year-old man suddenly developed severe dyspnea without cardiac failure. Radiographs and computed tomography of the chest showed pulmonary edema. A diagnosis of primary medullary hemorrhage was made some weeks later by cranial magnetic resonance imaging showing an area of low signal intensity in both T1- and T2-weighted images in the right ventrolateral, medial, and dorsal medulla, extending from low to mid levels. We suspect that edema surrounding the lesion had superimposed an element of left dorsal medullary dysfunction and that bilateral dorsal medullary involvement had induced neurogenic pulmonary edema.