29 Neurosurgery Treatment for Anorexia Nervosa
Abstract
Anorexia nervosa (AN) is one of the most challenging of the psychiatric disorders to treat. However, the poor clinical outcome of medical therapy in severe cases warrants the consideration of novel treatment modalities. Magnetic resonance imaging-guided bilateral anterior capsulotomy has been a long-standing approach for patients with severe obsessive-compulsive disorder (OCD). Because of the homogeneity between OCD and AN, and their comorbidity, capsulotomy has been used for enduring cases of AN. Deep brain stimulation (DBS) of the nucleus accumbens/ventral capsule and subcingulate region has also been used in a few cases. DBS’s implantable requirement, however, limits its use in patients with low bodyweight as is seen in AN. Capsulotomy can enable those patients in life threatening condition, with refractory AN, to normalize their weight. While it may be an acceptable life-saving treatment, it is indicated only when patients fulfill strict criteria, given the complications and irreversibility of surgery.
29.1 Patient Selection
Patients are diagnosed by independent psychiatrists, according to the DSM-IV criteria rather than DSM-5 criteria. The latter provides a broader definition of the disease entity. 1 , 2 If AN persists longer than seven years, it is likely that the disease has plateaued. 3 Thus, in the authors’ series, disease duration prior to surgery was usually more than 3 years, though the degree of disability was also considered
Patients must be eighteen years or older.
Patients are resistant to standard medicine and to psychotherapy treatments. Adequacy is defined as having been treated with at least two selective serotonin re uptake inhibitors, with anti-psychotics as augmentation, for at least twelve weeks at maximum tolerable dosage, and evidence-based psychotherapy conducted by an experienced therapist for three months. 4
Patients are in a life-threatening situation, defined as a physiological state with a BMI ≤ 13, or if they have attempted suicide.
Patients, together, with/without their legal representative, have the ability and willingness to provide informed consent.
Patients have normal fluid and electrolyte balance, and do not have a coagulopathy as measured by activated partial thromboplastin time and international normalized ratio.
Exclusion Criteria:
Medical contraindication to neurosurgery.
Inability to undergo MR imaging study.
Presence of a metabolic disease, such as diabetes, rather than an idiopathic psychiatric disorder alone.
29.2 Preoperative Preparation
Because of long-term malnutrition, general anesthesia or surgery may be contraindicated. Anorexia Nervosa (AN) patients are prone to electrolyte disturbances, cardiac failure, abnormal liver function, and coagulation abnormalities. 5 , 6 For such patients, extensive preoperative screening that should include electrocardiograms and coagulopathy testing is essential. Hypokalemia and hypoalbuminemia are the most common electrolyte disorders and these should be normalized. Most patients with AN have psychiatric comorbidities such as OCD, depression, anxiety, and even suicidal ideation. The mental status of AN patients is often unstable and patients frequently present with major depression. Thus, patients must be closely monitored throughout the entire procedure.
29.2.1 Intraoperative Management
Local anesthesia is recommended so as to avoid hypervolemia and excessive electrolytes dilution. For DBS, when general anesthesia is required, doses of anesthetic drugs should be adjusted for weight and, during the operation, electrocardiographic changes and potassium levels should be monitored carefully to minimize the risk of arrhythmias.
Because the skull of AN patients is usually thinned from bone rarefaction, burr holes can be dangerous and lead to epidural hematomas. To avoid excessive cerebrospinal fluid drainage, fibrin glue should be applied immediately after opening the dura. A warm air blower is helpful during surgery to maintain normal body temperature. Appropriate padding should be applied to all pressure points to avoid the higher risk of skin sores in these patients.
29.3 Operative Procedure
29.3.1 Capsulotomy
A stereotactic frame is mounted on the patient’s head under local anesthesia or mild sedation. Following frame placement, a 1.5 Tesla MRI is obtained. The targeted internal capsule is identified on the stereotactic MRIs. Target coordinates are calculated and the trajectory angle measured. Bilateral burr holes are drilled anterior to the coronal suture based on the measured entrance trajectory. The anterior capsule target is located between the anterior and middle third of the anterior limb of the internal capsule, as defined in MR images at the approximate level of the foramen of Monro. After dural opening and cauterization of the pia-arachnoid, a 2-mm diameter radiofrequency electrode with a 2-mm uninsulated tip is used for impedance measurement, followed by a stimulation test and lesioning. The radiofrequency lesions are generated by ablation at 75 degrees centigrade for 60 seconds. During lesioning, neurological examination is repeated to ensure that there is no impairment of motor or sensory functions. After adequate cooling, the electrode is withdrawn by 2 mm and the ablation procedure is repeated 4–5 times to ensure complete ablation of the anterior limb of the internal capsule. A lesion 4–5 mm in diameter and 10–12 mm in length along the contoured target is thus produced (▶ Fig. 29.1). Post-operative MRIs are obtained one week after surgery to confirm the lesion sites.
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