Preoperative Workup

Once the need for surgery has been determined the minimum surgical workup for every patient includes the following.

Endocrine Assessment

Endocrine assessment has two goals:

1. First, the surgeon and the endocrinologist must be sure of an accurate endocrine diagnosis before proceeding with surgery. In cases of hormone excess, it is essential to have adequate evidence of a pituitary source. It should not be assumed that all referring physicians will have completed the appropriate tests before referral. Aside from the risks to the patient of unnecessary pituitary exploration, the surgeon aquires an apparent surgical failure which is really a failure to investigate.

Measurement of serum prolactin (PRL) is mandatory. This is required to identify hyperprolacinemia attributable to a prolactinoma that usually responds to medical treatment with a dopamine agonist and spares the patient an operation. Thyroid function must also be assessed. It is dangerous to operate on a hypothyroid patient (see next paragraph). Also, rarely, a large pituitary lesion, apparently a tumor, may result from thyrotroph hyperplasia secondary to primary hypothyroidism. The MRI appearances in Fig. 1 were seen in such a case and resolved after thyroid replacement.

2. Second, the identification and treatment of hormone deficiency is required to optimize the safety of the anesthetic. Thyroxine and cortisol levels are the most important variables. The patient with myxoedema is at risk for a perioperative thyroid crisis if not placed on adequate replacement. If preoperative hypocortisolemia is present, then hydrocortisone replacement is essential.

Pituitary Hyperplasia

Fig. 1. Coronal T1 MRI shows a mass extending into the suprasellar space and displacing the chiasm. A 16-yr-old girl with a pituitary lesion confirmed as thyrotroph hyperplasia on histology. TSH was 27.1 mU/L.

Pituitary Hyperplasia Mri

Fig. 1. Coronal T1 MRI shows a mass extending into the suprasellar space and displacing the chiasm. A 16-yr-old girl with a pituitary lesion confirmed as thyrotroph hyperplasia on histology. TSH was 27.1 mU/L.

ChartingVisual Fields

Unless the tumor is entirely intrasellar, charting visual fields should always be done to both detect subclinical field defects and to act as a baseline investigation for the future. The automated Humphrey chart is internationally standardized and is satisfactory for identifying the bitemporal hemianopia characteristic of field loss from a chiasmal cause or more subtle quadrantic defects.

Imaging

Apart from its diagnostic role, preoperative imaging provides anatomical information to ensure a safe approach to the fossa from either below or above. The shape and consistency of the surgical target must be known and any atypical anatomy, especially a deviated midline sphenoid septum, recognized.

A high-quality MRI should always be obtained. The normal gland seen on MRI can change throughout life. Through most of life the normal gland is contained within the fossa without any upward bowing of the upper surface of the gland (Fig. 2).

In pregnancy and during the teenage growth spurt, the gland enlarges and it is quite possible to extend into the suprasellar space and even touch the chiasm. Hypertrophy from other causes also occurs rarely, for instance in primary hypothyroidism (Fig. 1). The gland may also be squeezed up into the suprasel-

Cavernous Sinus Meningioma
Fig. 2. (A) Normal gland in 32-yr-old woman. MRI T1 coronal image. Note small cavernous sinus meningioma on left. (B) T1 coronal with gadolinium, 1 mm posterior, to image (A). Note the pituitary stalk.

lar space by inturning of the carotid syphon in the cavernous sinus, the so-called kissing carotids (Fig. 3).

Kissing Carotid
Fig. 2. (C) Sagittal T1 MRI with enhancement of same patient, note posterior lobe is hyperintense.
Sagittal Mri Hypothalamus Germinal Tumor
Fig. 3. T-enhanced coronal MRI. Right internal carotid extending to midline in the pituitary fossa.

It is also possible to have completely normal pituitary function with an enlarged "ballooned" fossa, such as may be found in macroadenomas. Whether this reflects a tumor that has at some stage infarcted, leaving the normal gland intact or ballooning through chronic raised pressure of mild asymptomatic pseudo-tumor cerebri, is unknown. The posterior lobe has high signal intensity on Tl-weighted images. Although it is customary to give contrast medium, it often adds little to the value of the images.

Computed tomography (CT) is useful in difficult cases, particularly where there has been bone removal at a previous operation. The lateral skull radiograph is obsolete as part of the workup, being of low sensitivity, but the skill of interpreting the skull radiograph is essential to the surgeon when using intraoperative fluoroscopy. For all our revision cases, we employ an interactive image guidance system.

A Note on Pituitary Apoplexy

Because they present with acute symptoms, patients with pituitary apoplexy are commonly referred directly to the neurosurgical unit with minimum prior investigation. The key point regarding these patients is that they require the same high standard of preparation as elective cases, including identification and correction of any hormone deficit and satisfactory imaging. Steroids are administered to both treat deficiency of the hypothalamic-pituitary-adrenal (HPA) axis and diminish peritumoral swelling. Patients are sometimes gravely ill with a combination of panhypopituitarism, subarachnoid hemorrhage, and oculomotor palsies; it is misguided to embark on an urgent decompression without a full workup to minimize the risks of surgery. An operation within 24 to 48 h is satisfactory once endocrine and electrolyte abnormalities are corrected; emergency surgery out of hours is almost never indicated.

Once the patient is prepared, an operation promotes resolution of headache and recovery of cranial nerve deficits. The outlook for visual acuity after surgery is good. In a study of 35 patients by Randeva et al., complete restoration of visual acuity occurred in all patients operated on within 8 d (1).

When headache alone is the predominant symptom it is sometimes advisable to await a natural recovery. This may be the correct course, even when there is a coexisting third nerve palsy. The third nerve is surprisingly robust and can sometimes recover over days without any operative intervention. There may then be a role for a delayed operation to remove the tumor remnant and confirm the diagnosis.

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Responses

  • sandra
    WHAT IS intermaxillary space?
    7 years ago
  • Adelmio
    Is kissing carotids dangerous?
    7 years ago

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