Nelson’s syndrome

Nelson’s syndrome

Nelson’s syndrome is a rare and challenging neuroendocrine disorder, and it is associated with elevated Adrenocorticotropic hormone (ACTH) level, skin hyperpigmentation, and pituitary adenoma growth.

Key concepts

● a rare condition that follows 10–30% of total bilateral adrenalectomies (TBA) performed for Cushing’s disease.

● classic triad: hyperpigmentation (skin &mucus membranes), abnormal ↑ ACTH, and progression of pituitary tumor (the last criteria is now controversial)

● treatment options: surgery (transsphenoidal or transcranial), XRT, medication.

Usually occurs 1–4 years after TBA (range: 2 mos-24 years) 1). Theoretical explanation (unproven) 2): following TBA, hypercortisolism resolves, and CRH levels increase back to normal from the (reduced) suppressed state; corticotroph adenomas in patients with NS have an increased & prolonged response to CRH resulting in increased growth. Also, corticotrophs in NS and CD show reduced inhibition by glucocorticoids. It is controversial if some cases may be related to insufficient glucocorticoid replacement after TBA 3).

Clinical features

1. hyperpigmentation (due to melanin stimulating hormone (MSH) cross reactivity of ACTH and actual increased levels of MSH due to increased proopiomelanocortin production). Often the earliest sign that Nelson’s syndrome is developing. Look for linea nigra (midline pigmentation from pubis to umbilicus) and hyperpigmentation of scars, gingivae, and areolae. DDx of hyperpigmentation includes: primary adrenal insufficiency (high levels of ACTH), ectopic ACTH secretion, hemochromatosis (more bronze color), jaundice (yellowish)

2. tumor growth →increased mass effect or invasion: the most serious consequence. These corticotroph tumors are among the most aggressive of pituitary tumors 4). May produce any of the problems associated with macroadenomas (optic nerve compression, cavernous sinus invasion, pituitary insufficiency, H/A, bony invasion…) as well as necrosis with precipitous intracranial hypertension 5); see pituitary apoplexy.

3. malignant transformation of the corticotroph tumor (very rare).

4. hypertrophy of adrenal tissue rests: may be located in the testes → painful testicular enlargement and oligospermia. Rarely the rests can secrete enough cortisol to normalize cortisol levels or even cause a recurrence of Cushing’s disease despite the adrenalectomy.

Diagnosis

1. Laboratories

a) ACTH > 200 ng/L (usually thousands of ng/L)(normal:usually < 54 ng/L)

b) exaggerated ACTH response to CRH (not required for diagnosis)

c) other pituitary hormones may be affected as with any macroadenoma causing mass effect and endocrine screening should be done

2. Formal visual field testing: should be done in patients with suprasellar extension or in those being considered for surgery (as a baseline for comparison)

Treatment

Management options including resection and medical therapy are traditional approaches. Ionizing radiation in the form of Gamma Knife radiosurgery (GKRS) is also being utilized to treat Nelson’s syndrome. In a study Cordeiro et al., sought to better define the therapeutic role of stereotactic radiosurgery (SRS) in Nelson’s syndrome.

Study patients with Nelson’s syndrome were treated with single-fraction GKRS (median margin dose of 25 Gy) at 6 different centers as part of an International Radiosurgery Research Foundation (IRRF) investigation. Data including neurological function, endocrine response, and radiological tumor response were collected and sent to the study-coordinating center for review. Fifty-one patients with median endocrine and radiological follow-ups of 91 and 80.5 months from GKRS, respectively, were analyzed for endocrine remission, tumor control, and neurological outcome. Statistical methods were used to identify prognostic factors for these endpoints.

At last follow-up, radiological tumor control was achieved in 92.15% of patients. Endocrine remission off medical management and reduction in pre-SRS ACTH level were achieved in 29.4% and 62.7% of patients, respectively. Improved remission rates were associated with a shorter time interval between resection and GKRS (p = 0.039). Hypopituitarism was seen in 21.6% and new visual deficits were demonstrated in 15.7% of patients.

GKRS affords a high rate of pituitary adenoma control and improvement in ACTH level for the majority of Nelson’s syndrome patients. Hypopituitarism is the most common adverse effect from GKRS in Nelson’s syndrome patients and warrants longitudinal follow-up for detection and endocrine replacement 6).

References

1) , 3)

Banasiak MJ, Malek AR. Nelson syndrome: comprehensive review of pathophysiology, diagnosis, and management.Neurosurg Focus.2007;23
2)

Assie G, Bahurel H, Coste J, Silvera S, Kujas M, Dugue MA, et al. Corticotroph tumor progression after adrenalectomy in Cushing’s Disease: a reappraisal of Nelson’s syndrome. J Clin Endocrinol Metab. 2007; 49:381–386
4)

Bertagna X, Raux-Demay M-C, Guilhaume B, et al., Melmed S. In: Cushing’s Disease. The Pituitary. 2nd ed. Malden, MA: Blackwell Scientific; 2002:496–560
5)

Kasperlik-Zaluska AA, Bonicki W, Jeske W, Janik J, et al. Nelson’s syndrome – 46 years later: clinical experience with 37 patients. Zentralbl Neurochir. 2006; 67:14–20
6)

Cordeiro D, Xu Z, Li CE, Iorio-Morin C, Mathieu D, Sisterson ND, Kano H, Attuati L, Picozzi P, Sheehan KA, Lee CC, Liscak R, Jezkova J, Lunsford LD, Sheehan J. Gamma Knife radiosurgery for the treatment of Nelson’s syndrome: a multicenter, international study. J Neurosurg. 2019 Jul 12:1-6. doi: 10.3171/2019.4.JNS19273. [Epub ahead of print] PubMed PMID: 31299652.

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About the Clinical Editors

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Robotic pedicle screw placement learning curve

Robotic pedicle screw placement learning curve

Siddiqui et al., described the learning curve of pedicle screw placement using Robot-Assisted Spine Surgery (RASS) of an experienceneurosurgeon and two supervised neurosurgical fellows.

The first 120 cases of RASS at the University of Texas Health Science Center at San Antoniowere assessed. Patient variables included agebody mass index (BMI), and indication for surgery. Intra-operative variables included the vertebral level of pedicle screw placement, number of screws placed by each operator, intraoperative blood loss, and operative time. Post-operative variables included Length of stay (LOS), discharge disposition, 30-day readmissions, wound complications, and hardware revisions. Screw accuracy was determined with image overlay analysis comparing planned screw trajectory on the navigation software to the intra-operative CT scan with final screw placement. 2-dimensional accuracy was determined for the tip of the screw, tail of the screw, and angle the screw was placed. The supervising physician and first fellow began utilizing the robot concurrently upon its arrival, while the second fellow began using the robot after the system had been in place for seven months.

Both experienced surgeon and first fellow displayed a learning curve and achieved statistically significant improvement of accuracy after 30 screws. The second fellow had significantly better accuracy than the experienced surgeon in his first 30 screws. There were no complications from hardware placement in either group. There were no returns to the operating room for hardware issues.

RASS is a safe, accurate method of pedicle screw instrumentation. This data shows similar learning adaptation rates for the first fellow and the experienced surgeon. Techniques learned by attending were immediately transferable to a new learner, who was able to achieve a faster learning curve than both first fellow and experienced surgeon 1).


A major peak in screw inaccuracies occurred between cases 10 and 20, and a second, smaller one at about 40 surgeries. One potential explanation could be a transition from decreased supervision (unskilled but aware) to increased confidence of a surgeon (unskilled but unaware) who adopts this new technique prior to mastering it (skilled). Schatloet al., therefore advocate ensuring competent supervision for new surgeons at least during the first 25 procedures of robotic spine surgery to optimise the accuracy of robot-assisted pedicle screws 2).


Between June 2010 and August 2012, the senior surgeon (IHL) performed 174 posterior spinal procedures using pedicle screws, 162 of which were attempted with robotic assistance. The use of the robotic system was aborted in 12 of the 162 procedures due to technical issues (registration failure, software crash, etc). The robotic system was successfully used in the remaining 150 procedures. These were the first procedures performed with the robot by the senior surgeon, and in this study, we divided the early learning curve into five groups: Group 1 (Patients 1-30), Group 2 (Patients 31-60), Group 3 (Patients 61-90), Group 4 (Patients 91-120), and Group 5 (Patients 121-150). One hundred twelve patients (75%) had spinal deformity and 80 patients (53%) had previous spine surgery. The accuracy of screw placement in the groups was assessed based on intraoperative biplanar fluoroscopy and postoperative radiographs. The results from these five groups were compared to determine the effect on the learning curve. The numbers of attempted pedicle screw placements were 359, 312, 349, 359, and 320 in Groups 1 to 5, respectively.

The rates of successfully placed screws using robotic guidance were 82%, 93%, 91%, 95%, and 93% in Groups 1 to 5. The rates of screws converted to manual placement were 17%, 7%, 8%, 4%, and 7%. Of the robotically placed screws, the screw malposition rates were 0.8%, 0.3%, 1.4%, 0.8%, and 0%.

The rate of successfully placed pedicle screws improved with increasing experience. The rate of the screws that were converted to manual placement decreased with increasing experience. The frequency of screw malposition was similar over the learning curve at 0% to 1.4%. Future studies will need to determine whether this finding is generalizable to others 3).

References

1)

Siddiqui MI, Wallace DJ, Salazar LM, Vardiman AB. Robot-assisted pedicle screw placement is safe and accurate in both experienced and two supervised, in-training surgeons. World Neurosurg. 2019 Jun 24. pii: S1878-8750(19)31659-6. doi: 10.1016/j.wneu.2019.06.107. [Epub ahead of print] PubMed PMID: 31247356.
2)

Schatlo B, Martinez R, Alaid A, von Eckardstein K, Akhavan-Sigari R, Hahn A, Stockhammer F, Rohde V. Unskilled unawareness and the learning curve in robotic spine surgery. Acta Neurochir (Wien). 2015 Oct;157(10):1819-23; discussion 1823. doi: 10.1007/s00701-015-2535-0. Epub 2015 Aug 19. PubMed PMID: 26287268.
3)

Hu X, Lieberman IH. What is the learning curve for robotic-assisted pedicle screw placement in spine surgery? Clin Orthop Relat Res. 2014 Jun;472(6):1839-44. doi: 10.1007/s11999-013-3291-1. PubMed PMID: 24048889; PubMed Central PMCID: PMC4016454.
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