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Thread: Pallidotomy case pictures - NEURORADIOLOGY ATLAS

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    Default Pallidotomy case pictures - NEURORADIOLOGY ATLAS

    Summary
    We report a case of gamma knife pallidotomy resulting in a permanent contralateral homonymous hemianopsia and transient contralateral hemiparesis with some improvement in contralateral parkinsonian symptoms. This case illustrates the risk of gamma knife pallidotomy which precludes physiologic target localization and can subject structures surrounding the target to a significant radiosurgical dose. Until noninvasive physiologic target localization is available gamma knife pallidotomy and thalamotomy should be limited to patients with an unacceptably high risk for stereotactic percutaneous thermocoagulation.

    Hemiballismus is a relatively rare movement disorder that is characterized by uncontrolled, random, large-amplitude movements of the limbs. It is usually caused by a vascular lesion that involves the contralateral subthalamic nucleus (STN) (also known as the nucleus hypothalamicus or corpus luysi) and its afferent and efferent pathways.

    The authors present a case of medically intractable hemiballismus in a 70-year-old woman who was successfully treated with stereotactic posteroventral pallidotomy. In agreement with the data reported earlier by other groups, the microrecording performed during the pallidotomy showed a decreased rate of firing of the pallidal neurons, supporting the theory of impaired excitatory input from the STN to the internal part of the globus pallidus.


    Stereotactic pallidotomy may be the procedure of choice in the treatment of medically intractable hemiballismus. Intraoperative microrecording significantly improves the precision of the stereotactic targeting and should be considered a standard part of the pallidotomy protocol.

    Hemiballismus is a peculiar hyperkinetic disorder that appears as irregular and uncoordinated contorting movements of one half of the body, with a pronounced tendency to twist and turn. These movements are involuntary, violent, and poorly patterned. The syndrome of hemiballismus develops most commonly in patients with vascular or other injury of the STN and its connections. Despite the fact that hemiballismus is usually self-limiting and responsive to conservative treatment with neuroleptic, sedative, and other neuroactive medications, some patients with intractable disease are referred to neurosurgeons for surgical intervention.

    We present a case of medically intractable hemiballismus that was successfully treated with stereotactic posteroventral pallidotomy. In agreement with the data reported earlier by other groups, the microrecording performed during the pallidotomy showed a decreased rate of firing of the pallidal neurons, supporting the theory of impaired excitatory input from the STN to the GP

    This 70-year old woman with a history of hypertension and insulin-dependent diabetes mellitus presented with new onset of uncontrolled violent movements of the left extremities accompanied by headaches. Her symptoms started for no obvious reason; the movements were more pronounced in the arm than in the leg, and their amplitude increased over a period of 2 to 3 days after onset.
    Pallidotomy case pictures NEURORADIOLOGY ATLAS attachment.php?s=416aa617a438afafd8be2d4e1ce64a8c&attachmentid=1532&d=1440441961

    The patient was in good health on admission and results of her neurological examination were essentially normal except for the constant, relentless, violent movement of her left arm and leg. Although she was fully awake, alert, and oriented, she could not stop the abnormal movements except for a short period of time, and even then a major effort was required. Despite the protective cushioning that was applied to her bed to prevent injuries, both her left arm and leg were covered with bruises and lacerations. Attempts to restrain her from the flinging her extremities were also unsuccessful. The movements on the right side were unremarkable, but the patient could not perform any normal activity because of the left hemiballismus. All abnormal movements always stopped when she was asleep.

    Admission CT scans of the brain were obtained and revealed hypodensities in the right STN and the posterior limb of the left internal capsule (Fig. 1). Based on the clinical picture and CT appearance, we diagnosed a stroke involving the right STN.

    The patient's medical treatment consisted of a combination of neuroleptic agents (haloperidol, ≤ 10 mg/day) and benzodiazepines (lorazepam, ≤ 15 mg/day). This regimen only minimally decreased the abnormal movements but made the patient very somnolent. Chlorpromazine was also tried, but led to only a mild decrease in the frequency of ballistic movement. The patient's condition started to deteriorate because of severe exhaustion. She also required a feeding tube to get some nourishment. Surgery was recommended after the 10-day trial of conservative management failed.

    To prepare her for the pallidotomy, anesthesia was induced and the patient was intubated. A Leksell frame was applied, and the stereotactic magnetic resonance images were obtained using the standard protocol for pallidotomy. Axial T1-weighted, axial inversion-recovery, and coronal fast–spin echo magnetic resonance images were obtained. The GP, the internal capsule, and the optic tract were identified on both sides, and after that the stereotactic coordinates for the target point were calculated. The target was chosen at 19 mm to the right of the midline, 2 mm anterior to the midcommissural point, and 6 mm inferior to the plane of the anterior commissure– posterior commissure.

    After targeting was completed, the cannula was inserted through the twist-drill opening in the right precoronal region parallel to the sagittal plane and at a 65° angle to the axial plane. Microelectrode recording[44,45] was used to locate the GP externus, the internal medullary lamina, the GPi, and the optic tract. A total of six neurons was recorded, two in the GP externus and four in the GPi. The firing rate and pattern of the GPi neurons were somewhat different compared with those observed in patients with PD and patients with dystonias. The mean firing rate, for example, was 35 Hz as opposed to the mean GPi firing rate of 85 Hz described in the literature (Fig. 2). The kinesthetic response was elicited with passive movement of the left arm. The optic tract location was confirmed by stroboscopic stimulation. After completion of the microrecording, the standard method of radiofrequency thermocoagulation was used after heating the tip of the probe to 84°C for 60 seconds. A standard 1.1-mm-diameter probe with a 2-mm bare tip was used for the pallidotomy. Three lesions were made: one at the target point, one at 2 mm, and one at 4 mm superior to it along the trajectory of the electrode, and then the electrode and the cannula were removed.

    The patient exhibited no change in the severity of her ballistic movements immediately after the surgery. Over the next 24 hours, however, there was a gradual decrease in both amplitude and frequency of the abnormal movements. The patient maintained normal strength in all extremities and regained voluntary control over movements on the left side.

    At the follow-up examination 6 months postoperatively, the patient had returned to her normal activities, was able to walk without assistance, and all her bruises and abrasions gradually healed. She continued to have low-amplitude choreiform involuntary movements in the left leg, but this did not limit her functioning. More detailed examination revealed normal cranial nerves, no visual deficits, mild (4+/5) weakness in the left arm, and some disturbance of the gait with short steps and wide base. The walking problem had improved with physical therapy.

    References:
    Gamma knife pallidotomy: Case report - Springer
    Medscape: Medscape Access











    Last edited by Medical Photos; 08-24-2015 at 06:46 PM.

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