In: Main10 Dec 2009
This case indicates that SGB may relieve pain in some patients who are suspected to have symptomatic trigeminal neuralgia. SGB blocks sympathetic nervous activity to the head, neck, and upper extremity on the treated side. It is applied to reduce pain in patients with disor ders such as causalgia, reflex sympathetic dystrophies, peripheral vascular disease, acute herpes zoster, postherpetic neuralgia, and musculoskeletal disorders, and to improve certain vascular circulatory disorders.
In this case, the pain was noticeably relieved by SGB. Though the reasons why SGB was effective remain unclear, several mechanisms seem plausible. It is known that SGB induces changes in cerebral blood flow because the cerebral vasculature is believed to be under the control of sympathetic innervation. Ueyama et al showed an increase in the blood flow of the brain on the blocked side after SGB by single photon emission CT. It seems possible that if cerebral vasoconstriction played a role in intensification of painful symptoms, this might be partially reversed by SGB. It is known that intensely painful stimuli can excite the sympathetic nervous system. Theoretically, this may lead to peripheral vasoconstriction with associated cerebral vasculature contraction. Decreased local blood flow around the trigeminal nucleus may then lead to changes in neuronal activity. It is not clear how much cerebral blood flow autoregulation would negate this influence. More plausibly, tumor compression of local blood supply may be partially reversed by eliminating sympathetic control of cerebral blood flow through SGB. Increased blood flow to the region of compression may alter neuronal function to an extent that is sufficient to change pain perception. Another possible mechanism for symptom improvement may be a systemic local anesthetic effect. The systemic anesthetic property of mepivacaine might affect the hypersensitive nerves transiently, and the effects may linger after loss of the anesthetic effect. cialis professional
Another important aspect of diagnosis is highlighted by this case. Here, the CT images failed to reveal the lesion. Trigeminal neuralgia is frequently produced by lesions in the cerebellopontine angle. In the axial view, these lesions are often obstructed by bone artifacts in the skull base. To evaluate cerebellopontine angle le sions, useful information is better acquired in the coronal plane. Resolution by CT scanning is especially disadvantageous if the size of the tumor is small. Instead, MRI is preferable for detecting lesions in the brain stem because the resolution of the soft tissue is excellent without interference from bone artifacts. Additionally, in this case, despite the lack of intravenous enhancement application, the density of the tumor would have made detection difficult even with contrast. CT scanning is also disadvantageous for differentiating the tumor from CSF-containing cisterns adjacent to the region. However, if the tumor had produced bone destruction or calcification, CT scanning might have provided useful information that would supplement MRI.
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In this case, the patient’s symptoms were suggestive of trigeminal neuralgia, and were eventually diagnosed as being caused by an epidermoid tumor of the cerebellopontine angle. Before definitive diagnosis, SGB was utilized for pain relief. We conclude that SGB may provide relief to some patients with symptomatic trigeminal neuralgia.
Blog invites submissions of review articles, reports on clinical techniques, case reports, conference summaries, and articles of opinion pertinent to the control of pain and anxiety in dentistry.