Keiichi Amano

CT-guided stereotactic surgery for evacuation of hypertensive intracerebral hematoma

During the last 3 years, 46 cases of hypertensive intracerebral hemorrhage were treated by CT-guided stereotactic surgery. Our present report is concerned with the evaluation of this procedure in the treatment of hypertensive intracerebral hematoma, in terms of the rate of aspirated hematoma and follow-up study of patients. It is difficult to draw any definite conclusion about the operative indications. CT-guided stereotactic aspiration, however, can be evaluated as a less invasive and more definitive treatment of intracerebral hematoma in the basal ganglia and thalamus.

Single Neuron Analysis of the Human Midbrain Tegmentum

Rostral mesencephalic reticulotomy (RMR) has been performed since 1973 for relief of intractable pain. The target area is in the midbrain reticular formation (MRF) bordering the periaqueductal gray matter at the superior collicular level. The target of RMR is 13--16 mm posterior to the midpoint of the AC-PC line and 5--8 mm below the AC-PC line. The laterality of the target is measured from the center of the aqueduct, ranging 5 to 8 mm from the midline. The rationale for this procedure is based upon the previous findings that the brain stem reticular formation plays a more important role above the spinal cord level than the lateral spinothalamic tract in the central conduction of nociceptive impulse. In the present study, intraoperative single neuron recording was made with tungsten microelectrodes from the human midbrain tegmentum in response to peripheral pinprick stimulation. These nociceptive neurons were classified into three groups in regard to the unit latency from the peripheral pinprick stimulation.

Cervical kyphosis: Predictive factors for progression of kyphosis and myelopathy

Study Design. A retrospective study of 13 patients with cervical kyphosis. The authors propose new methods of measuring spinal cord compression and predicting the progression of kyphosis. Objectives. To ascertain predictive factors for progression of cervical kyphosis and myelopathy. Summary of Background Data. Cervical kyphosis may be congenital, result from decompression surgery, or occur as a posttraumatic deformity. Although there is the potential for progressive deformity and the development of myelopathy in all these situations, there are few previous reports of predictive factors for progression of cervical kyphosis and myelopathy in patients with cervical kyphosis. Methods. The authors studied radiographs and magnetic resonance imaging scans of 13 patients with cervical kyphosis, including 9 who had been operated on and had postsurgical secondary kyphosis, and 4 with idiopathic kyphosis without any of the above causes. Compression of the spinal cord at the apex of the cervical kyphosis was evaluated by magnetic resonance imaging of the ratio between the anteroposterior diameter of the medulla-pons junction and the spinal cord at the apex. Results. The mean ratio between the anteroposterior diameter of the medulla-pons junction and the spinal cord at the apex in five patients in whom myelopathy did not develop was 0.37, and was 0.21 in the patients in whom myelopathy developed. Progression of cervical kyphosis was associated with osteophyte formation at the anterior aspect of the vertebral body. Conclusion. A ratio below 0.3 between the anteroposterior diameter of the medulla-pons junction and the spinal cord at the apex was a risk factor for cervical myelopathy. One of the most predictable risk factors of progression of the cervical kyphosis was osteophyte formation at the anterior aspect of the vertebral body.

Alterations of Immunoreactive beta-Endorphin in the Third Ventricular Fluid in Response to Electrical Stimulation of the Human Periaqueductal Gray Matter

Immunoreactive beta-endorphin in the third ventricular fluid was measured in response to electrical stimulation of the periaqueductal gray matter in 8 patients with intractable pain during rostral mesencephalic reticulotomy for pain relief. In all patients, marked increase of immunoreactive beta-endorphin was observed. On the other hand, in cases of electrical stimulation of the zona incerta performed during stereoencephalotomy, in 5 patients with involuntary movement, immunoreactive beta-endorphin in the third ventricular fluid did not show any significant change. The authors conclude that the increase of immunoreactive beta-endorphin on electrical stimulation of the periaqueductal gray matter is not a nonspecific response to brain stimulation but a specific response in regard to cerebral localization of endorphins. Direct correlation between pain relief and periaqueductal gray stimulation is also questioned.

A New Apparatus for CT-Guided Stereotactic Surgery

Combining whole-body CT scan with a stereotactic system, the authors have developed and applied clinically an apparatus which readily provides intraoperative CT images, making it possible to confirm the location of the target point and ascertain the intraoperative environment. It takes about 9 s to obtain a CT image. Our purpose is to make stereotactic surgery, a kind of blind surgery, as safe and reliable as a visualized procedure by intraoperative CT scanning. By the method, in which there is very little invasion under local anesthesia, evacuation of deep-seated intracerebral hematomas as well as brain abscesses and also biopsy or brachytherapy of brain tumors in the brain can be done with safety and reliability.

Stereotactic Mesencephalotomy for Pain Relief

Rostral mesencephalic reticulotomy (RMR) for pain relief was performed in 34 patients with intractable pain. Most of these patients have been followed for a long period of time postoperatively, the longest follow-up period being 11 years. Contrary to the commonly prevailed bias in the past that mesencephalotomy may be a surgical intervention with potential risk, these patients of RMR have continued to substantial improvement postoperatively in terms of their preoperative intractable painful dysesthesia after a long period of time. The results of pain relief for denervation pain as well as for nondenervation pain are surprisingly good even after unilateral procedures. There was no operative mortality. Postoperative disturbance of ocular motility has been reduced. RMR has its scientific basis in that the medial part of the reticular formation rather than the classical lateral spinothalamic tract has more significance in the central conduction of nociceptive impulses through the midbrain level, which was verified by intraoperative neuronal recording with a tungsten microelectrode. The present report emphasizes that stereotactic mesencephalotomy, if performed meticulously and precisely, is a safe surgical procedure for pain relief. Results of MRI and sensory manifestations of a patient 11 years after RMR are also presented.

Spinal cord tissue oxygen in experimental ischemia, compression, and central necrosis.

A polarographic electrode of the surface reservoir type was applied to the canine cervical cord to obtain tissue oxygen tension. Normal, ischemic, compressed, and centrally necrotized spinal cords were examined. Effects of hypertension, hypotension, and pure oxygen inhalation on the cord oxygen were checked. Both ischemic and compressed cord demonstrated tissue oxygen lower than normal cord. Centrally necrotized cord showed normal oxygen in air ventilation but responded less markedly to 100% oxygen ventilation than did normal cord. Hypertension and hypotension made the cord oxygen rise and fall, respectively, more consistently in centrally necrotized cord than in normal cord. This method was shown to be useful for monitoring the spinal cord blood flow.

Cerebral-Evoked Responses Elicited by Direct Stimulation of the Lateral Spinothalamic Tract in the Human

The authors recorded cerebral-evoked responses elicited by direct stimulation of the human lateral spinothalamic tract (LST) during percutaneous cordotomy to investigate central conduction of noxious stimuli. These responses consisted of four negative potentials, peak latency being 3.8 (N1), 8.4 (N2), 12.2 (N3) and 21.9 (N4) ms respectively. N1 showed wide distribution over the scalp and was considered to be of subcortical origin. N2-N4 were distributed in both the temporal and central area. The different distribution pattern of N2-N4 from conventional somatosensory-evoked potential suggested a different projection of LST from the medial lemniscus system.

Somatotopic arrangement of lateral spinothalamic tract in percutaneous cervical cordotomy

As a new clinical approach for the purpose of mapping a lamina analysis, the present report deals with another landmark for insertion of the spinal needle in man other than the usual dentate ligament when performing a percutaneous cordotomy. Electrophysiological studies were made on 19 patients in order to determine the effect of electrostimulation with a bipolar concentric electrode, as well as to corroborate the position of the electrode radiologically. A new apparatus has been devised so that one can locate the target insertion point easily.

Role of Computerized Transverse Axial Tomography on Stereotactic Surgery of the Diencephalon

67 cases of various functional disorders of the diencephalon were examined by EMI scanner. The patients were composed of 38 cases of parkinsonism, 7 cases of thalamic syndrome, 6 cases of choreoathetoid movement, 2 cases of dystonia, 11 cases of involuntary movement of unknown etiology and 1 case of torticollis, tic, and ballismus, respectively. In parkinsonism, 79% showed diffuse cerebral atrophy, 5% had focal low density in the substantia nigra and the thalamus, whereas 16% remained normal. Pre- and postoperative assessment with CT scan was briefly discussed with reference to stereotactic surgery of the diencephalon.