Identification of the posterior lobe of the human pituitary gland during surgery using its electrophysiological, neural signature

Pituitary surgery is performed to remove adenomas. During pituitary surgery,
differentiating between anterior lobe, posterior lobe, and adenoma can be very
challenging, but extremely important because of the need for preservation of
the normal gland tissue and complete removal of the adenoma. In current
surgical technique only tissue consistency and colour are used to discriminate,
for which small incisions in, and manipulation of, the pituitary gland are
needed.
In the current study protocol we want to investigate if we can use the
electrophysiological properties of the posterior lobe, which consists of neural
axons from the hypothalamus, to reliably identify it. Electrical measurements
are done with microelectrodes, which are routinely used in clinical practice
for Deep Brain Stimulation (DBS). The electrical measurement is significantly
less traumatic than current surgical manipulation to inspect the gland. We
therefore expect that introduction of this technique will reduce the
complication rate of pituitary surgery, particularly the rate of diabetes
insipidus. Because pituitary cells of the anterior lobe also show electrical
activity, with different characteristics for each cell type, recording of the
electrical signature may also help with identification of adenoma tissue.

To record and analyse the electrophysiological properties and differences of
the human pituitary gland, i.e. the anterior lobe, posterior lobe and adenoma.

Observational, exploratory study

Use of the microTargeting electrodes is routine clinical practice in DBS
surgery. The overall risk of haemorrhage in DBS is 0-8%, most often reported as
1-2%. These haemorrhages are most often clinically not significant or cause
only temporary neurological deficits. In our study the electrode will be placed
directly into the pituitary tissue, without passing any brain tissue, therefore
the risk of a brain haemorrhage is zero. The risk of insertion only one
microelectrode is unknown, but will be lower because it is thinner than the
final DBS lead. When the risk of a pituitary haemorrhage is estimated to 2%,
this is significantly lower than the risk of tissue damage through surgical
manipulation. In our current series, postoperative diabetes insipidus, caused
by damage of the posterior lobe, occurs 20% temporary and 5% permanently. We
expect that already in the study population this incidence will be reduced
because of early and less traumatic identification of the posterior lobe.