Vernon H. Mark

STUDIES OF THE HUMAN THALAMUS: IV. EVOKED RESPONSES.

The increasing use of stereotactic surgery for the amelioration of chronic disabling orders of the central nervous system has provided the opportunity to record and stimulate the brain of conscious man. This important opportunity has been used capriciously by some investigators, while others have decried such studies as unjustifiable, unnecessary, or unrewarding. Both the fragmentary anecdotal material of the former and the neglect of the latter overlook a major responsibility of the investigator. Though he must avoid jeopardizing or exploiting the patient entrusted to his care, he has an obligation to attempt a systematic clarification of the pathophysiologic process involved so as to further the development of rational therapy. By adequately fulfilling this task, he should also provide an increasing insight into normal physiologic processes and their relationship to human behavior. Difficult as this task is amid the exigencies of clinical care, limited experimental paradigms, and restricted electrode placement, it is an increasingly important challenge to the neural scientist. Fortunately, the availability of multichannel tape recorders and increasingly sophisticated automatic techniques for signal analysis promises not only to simplify the task, but also to add an increasing depth of understanding to the data obtained. Our own studies include patients with intractable pain due to cancer of the head or neck, patients with the various movement disorders often attributed to basal ganglion dysfunction, and temporal lobe epileptics. The work reported here is from the former group of patients and is one aspect of our attempt to clarify the neural organization of “pain” and hopefully to add some information on somatosensory function in man.

Localized Cooling in the Brain

A slender refrigeration probe for the production of reversible discrete lesions within the central nervous system of man and experimental animals is described. Cooling, in the region of the third nerve nucleus in cats, produced pupillary dilatation which was quickly reversed when the temperature around the third nerve nucleus returned to normal.

Role of Thalamotomy in Treatment of Chronic Severe Pain

Bilateral thalamotomy may be effective when other neurosurgical procedures have failed to relieve chronic severe pain, such as pain secondary to advanced cancer. An illustrative case is described. Parafascicular electrodes are placed bilaterally even in cases of unilateral pain. In some cases it is unnecessary to add the destructive effect of radiofrequency current. Three clinical-anatomic syndromes representing the effects of surgically produced thalamic lesions are described. Each was reconstructed from examination of several similar cases in which a particular nuclear complex was the chief site of the lesions.

The destruction of both anterior thalamic nuclei in a patient with intractable agitated depression.

A patient with chronic intractable agitated depression resistant to psychotherapy, pharmacological agents, and electroshock therapy was presented. In spite of the mood elevation produced by anterior thalamic nucleus destructions, the patients impulse control was insufficient to prevent a suicide. A thorough examination of the patients brain made it possible to make an anatomical clinical correlation of anterior thalamic nucleus function.

Observations on the role of afferent and descending impulses on the spontaneous potentials of the spinal cord.

Abstract 1. 1. Changes in the spinal electrogram of cats were studied as a function of spinal cord transection under ether and Nembutal, and as a function of spinal cord isolation (i.e., complete dorsal root interruption to a segment of cord between two spinal cord transections). 2. 2. Animals with spinal cords transected under ether showed an average increase in amplitude of 33 per cent in 9 out of 12 animals transected. 3. 3. Animals with spinal cords transected under Nembutal anaesthesia showed no marked change in spinal electrogram. 4. 4. Activation of the nearly isolated spinal cord by stimulations of a single intact dorsal rootlet is demonstrated. 5. 5. Isolated spinal cord segments continued to generate the spinal electrogram at a reduced amplitude in both acute and chronic animals. 6. 6. Histological sections of the isolated spinal cord segments are reviewed.

Deep Temporal Lobe Stimulation in Man

Before discussing deep temporal lobe stimulation with chronically implanted stereotactic electrodes, it might be well to mention some of the ethical considerations involved in this kind of stereotactic surgery. First of all, the patients who are candidates for stereotactic temporal lobe electrodes are all temporal lobe epileptics with aggressive behavior who have had a considerable trial period of anti-epileptic and ataractic drugs, together with the various forms of psychotherapy. Almost all of these patients would be considered as candidates for the more traditional anterior temporal lobectomy, except that they had multiple foci, which were usually independent, bilateral, and non-synchronous in nature. All of our patients except one were adults, and this one exception was a brain tumor suspect with a pneumoencephalographic diagnosis of temporal lobe tumor.

The Study and Treatment, on a Neurological Ward, of Abnormally Aggressive Patients with Focal Brain Disease (Part 1 of 2)

Thirty-six patients with a history of aggressive violent behavior and/or limbic brain disease were studied on an open neurological-neurosurgical ward by psychiatrists, neurologists and neurosurgeons,

Further experiences with intrathecal phenol for the relief of pain

Abstract The intrathecal administration of phenol, which is a relatively simple procedure and relatively free of significant complications, has proved to be a useful adjunct in the treatment of chronic severe pain, especially pain secondary to inoperable malignancy. It has been particularly useful in (1) bathing the lower sacral rootlets bilaterally in perineal and perianal pain, (2) relieving severe pain in frankly terminal and debilitated cancer victims who are not relieved by narcotics, and (3) relieving unilateral upper abdominal and thoracic pain. Since 1961 a modified technique has been used to treat 31 patients with intrathecal phenol for the relief of chronic pain. In the 1958–1961 series, 87 patients had been treated, and the results of the two groups are compared. Qualitatively better results were obtained with the more recent group. These improved results are attributed to: 1. (1) The almost exclusive use of solutions of phenol in anhydrous glycerine in preference to solutions of phenol in Pantopaque (iophendylate). 2. (2) The use of a multiple injection technique. Significantly better results were achieved in the relief of pain secondary to cancer than in pain of non-cancer origin. Complications have included mild weakness and bladder difficulty; late scarring may make subsequent surgical rhizotomy difficult. Only 2 of the last 31 patients required subsequent chordotomy.

Sleep induced by focal brain suppression using anesthetic gases.

Abstract Silicone rubber tubing has been shown to be permeable to most anesthetic gases and has been used to fashion “chemodes” for stereotaxic intracerebral inplantation. The safety of these devices and their effectiveness in producing focal brain suppression was studied in cats with chronically implanted chemodes. The silastic chemodes were found to elicit little reaction after chronic implantation. When perfused through the chemodes, the anesthetic gas, Tefluorane, was found likewise to cause little cerebral reaction, while inducing satisfactory and reversible focal cerebral suppression. The effectiveness was evaluated in terms of sleep production with chemodes implanted in the reticular-activating system. Silastic rubber chemodes allow the focal introduction of various gases, liquids and solutions into the brain with no additional distortion of the brain. The membrane is impermeable to bacteria, so that nonsterile chemicals may be employed. This study demonstrated the safety of chronically implanting chemodes and their effectiveness in producing focal brain suppression. The use of brain stimulants as well as suppressants should make these devices useful for animal experimentation and human therapy.

STEREOTACTIC SURGERY: A NOTE ON INSTRUMENTATION

Stereotactic surgical instruments havedeveloped along twolines. Themoretraditional andaccurate machines weredevised bySpiegel andWycis (1952), Spiegel, Wycis, Marks, andLee(1947), Bailey and Stein (1951), Talairach, HeI-{aen, David, Monnier, and Ajuriaguerra (1949), Leksell (1949), Riechert,and Mundinger (1954), and others. Mostofthese machines arefixed totheskull for stability, andtheyemploy a variety ofgeometric methodsforcorrecting thedistortion andhead rotation occurring incranial radiographs. A stereotactic surgeon, utilizing oneofthese traditional machines withitsaccompanying method forcorrectingradiological distortion, isabletohita radiologically visualized intracranial target witha high degree ofaccuracy. (This leaves outentirely the question ofgeographic variation oftheanatomical target structures within theintracranial cavity in their relation topoints that canbevisualized byair oropaqueventriculography.) Unfortunately, most ofthetraditional stereotactic machines arecomplicated andtimeconsuming touse.Ontheother hand,Parera andCooper(1960) devised needle guiding machines, usedprincipally inthetreatment ofParkinsons disease. Thesemachines canbe applied quickly andeasily andsomeofthemare fixed totheskull. Their accuracy, however, isnotas great asthetraditional stereotactic machines, and they areoften usedinconjunction withuncorrected measurements takendirectly fromcranial radiographs. A stereotactic machine, likeanyothersurgical tool, requires constant refinement. Itwasfelt that astereotactic machine that combined theaccuracy of thetraditional, skull-fixed radiologically orientated machines withthesimplicity andflexibility ofthe needle guides wouldbeawelcome addition tothe neurosurgical armamentarium. In1954, ourgroupdescribed a newmethodfor correcting distortion incranial radiographs with special reference tothetypeIMcPherson stereotactic machine(Mark,McPherson, andSweet, 1954). Thismethod employs askull-fixed tubular aluminum stereotactic machinewithattachable leadgrids. Whenthedistances between thex-ray tube, thelead grid lines, andthex-ray plate arefixed, onecanusea geometric methodtoplottheposition ofany desired target point between thegrids, i.e., intracranial point. Withthis method, itispossible to correct themagnification error inherent inall cranial radiographs withrelatively short tube-film distances and,inaddition, compensate forthedegree of rotation ortilt ofthehead.Bymeansofthegeometric plots, itisthuspossible totranslate radiological measurements intosettings forthestereotactic machine that will hitagiven intracranial point withanerror ofless thanonehalf millimetre. Although this methodiseasytouse,thetype1 McPherson stereotactic machine itself iscumbersome.Thesurgical procedure withthismachine hastobedoneintwostages: onestags forthedrilling oftiny openings intheouter table oftheskull and theperformance ofaventriculogram, andthesecond stage fortheinsertion oftheelectrodes intothe target areas (Mark, Ervin, andHackett, 1960). The halo, utilized asthebaseofthestereotactic machine, completely surrounds theheadinawidebandand, therefore, limits thepossible positions andangles at whichanelectrode canenter thecranial vaults to reach anintracranial target. We decided, then, to design a newstereotactic machinewhichwould overcome thedefects ofthefirst modelwithout sacrificing itspotential accuracy.