Linezolid

Linezolid

MRSA and MRSE (with MIC > 1 mcg/ml) or patient with vancomycin allergy Linezolid 600mg IV or PO q 12 hrs

Linezolid is an antibiotic used for the treatment of serious infections caused by Gram positive bacteria that are resistant to other antibiotics. Linezolid is active against most Gram-positive bacteria that cause disease, including streptococci, vancomycin-resistant enterococci (VRE), and methicillin resistant Staphylococcus aureus (MRSA).

The main uses are infections of the skin and pneumonia although it may be use for a variety of other infections.

When administered for short periods, linezolid is a relatively safe antibiotic. It can be used in people of all ages and in people with liver disease or poor kidney function. Common adverse effects of short-term use include headache, diarrhea, and nausea. Long-term use, however, has been associated with serious adverse effects such as bone marrow suppression and low platelet counts, particularly when used for more than two weeks. If used for longer periods still, it may cause sometimes irreversible chemotherapy-induced peripheral neuropathy and optic nerve damage, and lactic acidosis (a buildup of lactic acid in the body), all most likely due to mitochondrial toxicity.

As a protein synthesis inhibitor, it stops the growth of bacteria by disrupting their production of proteins, that is, it is a bacteriostatic agent, not bacteriocidal. Although many antibiotics work this way, the exact mechanism of action of linezolid appears to be unique in that it blocks the initiation of protein production, and not one of the later steps.

Bacterial resistance to linezolid has remained very low since it was first detected in 1999, although it may be increasing. It is a member of the oxazolidinone class of drugs.

Linezolid was discovered in the 1990s by a team at Pharmacia and Upjohn Company and first approved for use in 2000. It is on the World Health Organization’s List of Essential Medicines, the most important medications needed in a basic health system.

Linezolid costs approximately US$100 per tablet in the United States. Nonetheless, it appears to be more cost-effective than generic alternatives such as vancomycin, mostly because of the possibility of switching from intravenous to oral administration as soon as patients are stable enough, without the need for dose adjustments.


In animal studies of meningitis caused by Streptococcus pneumoniae, linezolid was found to penetrate well into cerebrospinal fluid, but its effectiveness was inferior to that of other antibiotics.

There does not appear to be enough high-quality evidence to support the routine use of linezolid to treat bacterial meningitis. Nonetheless, it has been used successfully in many cases of central nervous system infection—including meningitis—caused by susceptible bacteria, and has also been suggested as a reasonable choice for this indication when treatment options are limited or when other antibiotics have failed.

The guidelines of the Infectious Diseases Society of America recommend linezolid as the first-line drug of choice for VRE meningitis, and as an alternative to vancomycin for MRSA meningitis.

Linezolid appears superior to vancomycin in treating community-acquired MRSA infections of the central nervous system, although very few cases of such infections have been published (as of 2009).

Effectiveness in Neurosurgery

Evidence for the effectiveness of linezolid in neurosurgical infections (NSIs) is growing. The comfortable oral dosage and tolerance of linezolid opens the possibility for sequential antimicrobial treatment (SAT) in stable patients after a period of intravenous treatment 1).

Reviews

Relevant studies were identified through searches of the PubMed, Current Contents, and Cochrane databases (publications archived until October 2006).

Case reports, case series, prospective and retrospective studies, and randomized controlled trials were eligible for inclusion in our review if they evaluated the effectiveness and safety of linezolid for the treatment of patients with CNS infections.

In 18 (42.9%) of the 42 relevant cases identified, patients had undergone neurosurgical operations and/or had prosthetic devices. Meningitis was the most common CNS infection, accounting for 20 (47.6%) cases. Other CNS infections included brain abscesses (14; 33.3%), ventriculitis (5; 11.9%), and ventriculo-peritoneal shunt infection (3; 7.1%). In the 39 patients in whom the responsible pathogen was isolated, those predominantly responsible for the CNS infections were: penicillin-nonsusceptible Streptococcus pneumoniae (7; 17.9%), vancomycin-resistant enterococci (6; 15.4%), Nocardia spp. (5; 12.8%), methicillin-resistant Staphylococcus epidermidis (4; 10.3%), and methicillin-resistant Staphylococcus aureus (3; 7.7%). Of the 42 patients who received linezolid for the treatment of CNS infections, 38 (90.5%) were either cured or showed clinical improvement of the infection. The mean duration of follow-up was 7.2 months; no recurrent CNS infection was reported.

The limited published data suggest that linezolid may be considered for the treatment of patients with CNS infections in cases of failure of previously administered treatment or limited available options 2).

Case series

To evaluate the efficacy and safety of SAT with oral linezolid in patients with NSI and to analyse the cost implications, an observational, non-comparative, prospective cohort study was conducted on clinically stable consecutive adult patients at the Neurosurgical Service. Following intravenous treatment, patients were discharged with SAT with oral linezolid.

A total of 77 patients were included. The most common NSIs were: 41 surgical wound infections, 20 subdural empyemas, 18 epidural abscesses, and 16 brain abscesses. Forty-four percent of patients presented two or more concomitant NSIs. Aetiological agents commonly isolated were: Propionibacterium acnes (36 %), Staphylococcus aureus (23 %), Staphylococcus epidermidis (21 %) and Streptococcus spp. (13 %). The median duration of the SAT was 15 days (range, 3-42). The SAT was interrupted in five cases due to adverse events. The remainder of the patients were cured at the end of the SAT. A total of 1,163 days of hospitalisation were saved. An overall cost reduction of €516,188 was attributed to the SAT. Eight patients with device infections did not require removal of the device, with an additional cost reduction of €190,595. The mean cost saving per patient was €9,179.

SAT with linezolid was safe and effective for the treatment of NSI. SAT reduces hospitalisation times, which means significant savings of health and economic resources 3).

References

1)

Jahoda D, Nyc O, Pokorný D, Landor I, Sosna A. [Linezolid in the treatment of antibiotic-resistant gram-positive infections of the musculoskeletal system]. Acta Chir Orthop Traumatol Cech. 2006 Oct;73(5):329-33. Czech. PubMed PMID: 17140514.
2)

Ntziora F, Falagas ME. Linezolid for the treatment of patients with central nervous system infection. Ann Pharmacother. 2007 Feb;41(2):296-308. Epub 2007 Feb 6. Review. PubMed PMID: 17284501.
3)

Martín-Gandul C, Mayorga-Buiza MJ, Castillo-Ojeda E, Gómez-Gómez MJ, Rivero-Garvía M, Gil-Navarro MV, Márquez-Rivas FJ, Jiménez-Mejías ME. Sequential antimicrobial treatment with linezolid for neurosurgical infections: efficacy, safety and cost study. Acta Neurochir (Wien). 2016 Oct;158(10):1837-43. doi: 10.1007/s00701-016-2915-0. Epub 2016 Aug 13. PubMed PMID: 27520361.

5-aminolevulinic-acid guided resection

5-aminolevulinic-acid guided resection

In addition to stereotactic localization as well as intraoperative brain mapping, techniques to enhance visual identification of tumor intraoperatively may be used and include 5-aminolevulinic-acid (5-ALA). 5-ALA is metabolized into fluorescent porphyrins, which accumulate in malignant glioma cells. These property permits use of ultraviolet illumination during surgery as an adjunct to map out the tumor. This has been proven with RCT where the use of 5-ALA leads to more complete resection (65% vs. 36%, p < 0.0001), which translates into a higher 6-month progression-free survival (41% vs. 21.1%, p = 0.0003) but no effect on OS 1).


Fluorescein can be used as a viable alternative to 5-ALA for intraoperative fluorescent guidance in brain tumor surgery. Comparative, prospective, and randomized studies are much needed 2).


Indications

Meningeal sarcoma

First case published in the literature of meningeal sarcoma in a child in which intraoperative fluorescence with 5-ALA was used to achieve a complete resection 5).

Meningioma

Metabolic imaging tools such as 5-ALA fluorescence-guided resection and navigated FET-PET were helpful for the resection of complex-shaped, recurrent skull base meningioma. 5-ALA fluorescence was useful to dissect the adherent interface between tumor and brain. Furthermore, it helped to delineate tumor margins in the nasal cavity. FET-PET improved the assessment of bony and dural infiltration. We hypothesize that these imaging technologies may reduce recurrence rates through better visualization of tumor tissue that might be left unintentionally. This has to be verified in larger, prospective trials 6).

Tumor fluorescence can occur in benign meningiomas (WHO grade I) as well as in WHO grade II and WHO grade III meningiomas. Most of the reviewed studies report fluorescence of the main tumor mass with high sensitivity and specificity. However, different parts of the same tumor can present with a different fluorescent pattern (heterogenic fluorescence). Quantitative probe fluorescence can be superior, especially in meningiomas with difficult anatomical accessibility. However, only one study was able to consistently correlate resected tissue with histopathological results and nonspecific fluorescence of healthy brain tissue remains a confounder. The use of 5-ALA as a tool to guide resection of intracranial meningiomas remains experimental, especially in cases with tumor recurrence. The principle of intraoperative fluorescence as a real-time method to achieve complete resection is appealing, but the usefulness of 5-ALA is questionable. 5-ALA in intracranial meningioma surgery should only be used in a protocolled prospective and long-term study 7).

Doses

The highest visible and measurable fluorescence was yielded by 20 mg/kg. No fluorescence was elicited at 0.2 mg/kg. Increasing 5-ALA doses did not result in proportional increases in tissue fluorescence or PPIX accumulation in plasma, indicating that doses higher than 20 mg/kg will not elicit useful increases in fluorescence 8).


Application of 5mg/kg ALA was evaluated as equally reliable as the higher dose regarding the diagnostic performance when guidance was performed using a spectroscopic system. Moreover, no PpIX was detected in the skin of the patients 9).

Over time, several other tumour entities have been identified to metabolize 5-ALA and show a similar fluorescence pattern during surgical resection.

Further research is warranted to determine the role of 5-ALA accumulation in post-ischaemic and inflammatory brain tissue 10).

The positive predictive values (PPVs), of utilizing the most robust ALA fluorescence intensity (lava-like orange) as a predictor of tumor presence is high. However, the negative predictive values (NPVs), of utilizing the absence of fluorescence as an indicator of no tumor is poor. ALA intensity is a strong predictor for degree of tumor cellularity for the most fluorescent areas but less so for lower ALA intensities. Even in the absence of tumor cells, reactive changes may lead to ALA fluorescence 11).

Reviews

Senders et al., systematically review all clinically tested fluorescent agents for application in fluorescence guided surgery (FGS) for glioma and all preclinically tested agents with the potential for FGS for glioma.

They searched the PubMed and Embase databases for all potentially relevant studies through March 2016.

They assessed fluorescent agents by the following outcomes: rate of gross total resection (GTR), overall and progression free survival, sensitivity and specificity in discriminating tumor and healthy brain tissue, tumor-to-normal ratio of fluorescent signal, and incidence of adverse events.

The search strategy resulted in 2155 articles that were screened by titles and abstracts. After full-text screening, 105 articles fulfilled the inclusion criteria evaluating the following fluorescent agents: 5 aminolevulinic acid (5-ALA) (44 studies, including three randomized control trials), fluorescein (11), indocyanine green (five), hypericin (two), 5-aminofluorescein-human serum albumin (one), endogenous fluorophores (nine) and fluorescent agents in a pre-clinical testing phase (30). Three meta-analyses were also identified.

5-ALA is the only fluorescent agent that has been tested in a randomized controlled trial and results in an improvement of GTR and progression-free survival in high-grade gliomas. Observational cohort studies and case series suggest similar outcomes for FGS using fluorescein. Molecular targeting agents (e.g., fluorophore/nanoparticle labeled with anti-EGFR antibodies) are still in the pre-clinical phase, but offer promising results and may be valuable future alternatives. 12).

Complications

Despite its benefits, 5-ALA has not reached widespread popularity in the United States, primarily because of lack of Food and Drug Administration (FDA) approval. Even if it were approved, 5-ALA does have specific limitations including low depth of penetration, autofluorescence of background parenchyma


Findings suggest that the administration of 5-ALA or the combined effect of 5-ALA, anaesthesia and tumour resection can cause a mild and reversible elevation in liver enzymes. It therefore appears safe to change the regime of monitoring. Routine blood samples are thus abolished, though caution remains necessary in patients with known liver impairment 13).

For near infrared imaging, additional investigators have explored fluorescein as well as novel near-infrared (NIR) agents 14) 15) 16)

Stummer et al. showed that 5–ALA guided resections carry a higher risk of post-operative neurological deterioration than conventional resections (26% vs 15%, respectively), even though the difference vanished within weeks 17).

Just as tumour tissue is often indiscernible from normal brain tissue, functionally critical tissues are indistinguishable from tissues with less clinically relevant functions.

Thus, knowing when to stop a resection due to proximity to areas of crucial neurological functions is of obvious and utmost importance. Detailed knowledge of the normal brain anatomy and distribution of function is not sufficient during glioma resection. Interindividual variability and functional relocation (i.e., plasticity) induced by the presence of an infiltrating tumour 18) requires an exact functional brain map at the site of surgery in order to spare areas involved in crucial (so-called eloquent) functions. Preoperative localisation of function, either with functional MRI (fMRI) or navigated transcranial magnetic stimulation (nTMS), provides an approximate map 19) 20).

Furthermore, intra-operative direct cortical and subcortical electrical stimulation (DCS) for functional analysis of the tissue in the tumour’s infiltration zone is required for accurate identification of areas that need to be spared in order to retain the patient’s functional integrity 21) 22). Motor evoked potentials (MEP) provide real-time information on the integrity of the primary motor cortex and the corticospinal tract 23). Direct cortical mapping and phase reversal identify the primary motor and sensory cortices. Subcortical mapping can estimate the distance to the pyramidal tract, acting as guidance close to functionally critical areas 24). When integrated into the existing surgical tools, continuous and dynamic mapping enables more extensive resection while simultaneously protecting motor function 25). Using these techniques and a detailed electrophysiological “Bern-concept”, a group achieved complete motor function protection in 96% of patients with high-risk motor eloquent tumours 26). Furthermore, localisation of cortical and subcortical regions relevant to language function is essential for speech preservation during resection of gliomas in proximity to presumed speech areas 27) and requires the patient to be awake during the brain mapping part of surgery. Similarly, intra-operative mapping of visual functions may contribute to increased resections while avoiding tissue essential for vision within the temporal and occipital lobes 28).

References

1) , 3)

Stummer W, Pichlmeier U, Meinel T, Wiestler OD, Zanella F, Reulen HJ; ALA-Glioma Study Group. Fluorescence-guided surgery with 5-aminolevulinic acid for resection of malignant glioma: a randomised controlled multicentre phase III trial. Lancet Oncol. 2006 May;7(5):392-401. PubMed PMID: 16648043.
2)

Hansen RW, Pedersen CB, Halle B, Korshoej AR, Schulz MK, Kristensen BW, Poulsen FR. Comparison of 5-aminolevulinic acid and sodium fluorescein for intraoperative tumor visualization in patients with high-grade gliomas: a single-center retrospective study. J Neurosurg. 2019 Oct 4:1-8. doi: 10.3171/2019.6.JNS191531. [Epub ahead of print] PubMed PMID: 31585425.
4)

Lakomkin N, Hadjipanayis CG. Fluorescence-guided surgery for high-grade gliomas. J Surg Oncol. 2018 Aug 19. doi: 10.1002/jso.25154. [Epub ahead of print] Review. PubMed PMID: 30125355.
5)

Bernal García LM, Cabezudo Artero JM, Royano Sánchez M, Marcelo Zamorano MB, López Macías M. Fluorescence-guided resection with 5-aminolevulinic acid of meningeal sarcoma in a child. Childs Nerv Syst. 2015 Apr 12. [Epub ahead of print] PubMed PMID: 25863951.
6)

Cornelius JF, Slotty PJ, Stoffels G, Galldiks N, Langen KJ, Steiger HJ. 5-Aminolevulinic Acid and (18)F-FET-PET as Metabolic Imaging Tools for Surgery of a Recurrent Skull Base Meningioma. J Neurol Surg B Skull Base. 2013 Aug;74(4):211-6. doi: 10.1055/s-0033-1342918. Epub 2013 Apr 1. PubMed PMID: 24436914.
7)

Motekallemi A, Jeltema HR, Metzemaekers JD, van Dam GM, Crane LM, Groen RJ. The current status of 5-ALA fluorescence-guided resection of intracranial meningiomas-a critical review. Neurosurg Rev. 2015 Mar 5. [Epub ahead of print] PubMed PMID: 25736455.
8)

Stummer W, Stepp H, Wiestler OD, Pichlmeier U. Randomized, Prospective Double-Blinded Study Comparing 3 Different Doses of 5-Aminolevulinic Acid for Fluorescence-Guided Resections of Malignant Gliomas. Neurosurgery. 2017 Apr 1. doi: 10.1093/neuros/nyx074. [Epub ahead of print] PubMed PMID: 28379547.
9)

Haj-Hosseini N, Richter J, Hallbeck M, Wårdell K. Low dose 5-aminolevulinic acid: Implications in spectroscopic measurements during brain tumor surgery. Photodiagnosis Photodyn Ther. 2015 Mar 25. pii: S1572-1000(15)00031-9. doi: 10.1016/j.pdpdt.2015.03.004. [Epub ahead of print] PubMed PMID: 25818546.
10)

Behling F, Hennersdorf F, Bornemann A, Tatagiba M, Skardelly M. 5-Aminolevulinic acid accumulation in a cerebral infarction mimicking high-grade glioma, a case report. World Neurosurg. 2016 May 10. pii: S1878-8750(16)30271-6. doi: 10.1016/j.wneu.2016.05.009. [Epub ahead of print] PubMed PMID: 27178236.
11)

Lau D, Hervey-Jumper SL, Chang S, Molinaro AM, McDermott MW, Phillips JJ, Berger MS. A prospective Phase II clinical trial of 5-aminolevulinic acid to assess the correlation of intraoperative fluorescence intensity and degree of histologic cellularity during resection of high-grade gliomas. J Neurosurg. 2015 Nov 6:1-10. [Epub ahead of print] PubMed PMID: 26544781.
12)

Senders JT, Muskens IS, Schnoor R, Karhade AV, Cote DJ, Smith TR, Broekman ML. Agents for fluorescence-guided glioma surgery: a systematic review of preclinical and clinical results. Acta Neurochir (Wien). 2017 Jan;159(1):151-167. doi: 10.1007/s00701-016-3028-5. Review. PubMed PMID: 27878374; PubMed Central PMCID: PMC5177668.
13)

Offersen CM, Skjoeth-Rasmussen J. Evaluation of the risk of liver damage from the use of 5-aminolevulinic acid for intra-operative identification and resection in patients with malignant gliomas. Acta Neurochir (Wien). 2016 Nov 10. [Epub ahead of print] PubMed PMID: 27832337.
14)

Shinoda J, Yano H, Yoshimura SI, et al. Fluorescence-guided resection of glioblastoma multiforme by using high-dose fluorescein sodium. Technical note. J Neurosurg. 2003;99(3):597–603.
15)

Rey-Dios R, Cohen-Gadol AA. Technical principles and neurosurgical applications of fluorescein fluorescence using a microscope-integrated fluorescence module. Acta Neurochir (Wien). 2013;155(4):701–706.
16)

Swanson KI, Clark PA, Zhang RR, et al. Fluorescent cancer-selective alkylphosphocholine analogs for intraoperative glioma detection. Neurosurgery. 2015;76(2):115–123.
17)

Stummer W1, Tonn JC, Mehdorn HM, Nestler U, Franz K, Goetz C, et al. ALA-Glioma Study Group. Counterbalancing risks and gains from extended resections in malignant glioma surgery: a supplemental analysis from the randomized 5–aminolevulinic acid glioma resection study. J Neurosurg. 2011;114(3):613–23. doi: 10.3171/2010.3
18)

Ojemann G, Ojemann J, Lettich E, Berger M. Cortical language localization in left, dominant hemisphere. An electrical stimulation mapping investigation in 117 patients. J Neurosurg. 1989;71(3):316–26.
19)

Seghier ML, Lazeyras F, Pegna AJ, Annoni JM, Zimine I, Mayer E, et al. Variability of fMRI activation during a phonological and semantic language task in healthy subjects. Hum Brain Mapp. 2004;23(3):140–55.
20)

Krieg SM, Shiban E, Buchmann N, Gempt J, Foerschler A, Meyer B, et al. Utility of presurgical navigated transcranial magnetic brain stimulation for the resection of tumors in eloquent motor areas. J Neurosurg. 2012;116(5):994–1001. doi: 10.3171/2011.12.JNS111524
21) , 27)

Duffau H, Capelle L, Sichez N, Denvil D, Lopes M, Sichez JP, et al. Intraoperative mapping of the subcortical language pathways using direct stimulations. An anatomo-functional study. Brain. 2002;125(1):199–214.
22)

Duffau H, Capelle L, Denvil D, Sichez N, Gatignol P, Taillandier L, et al. Usefulness of intraoperative electrical subcortical mapping during surgery for low-grade gliomas located within eloquent brain regions: functional results in a consecutive series of 103 patients. J Neurosurg. 2003;98(4):764–78.
23)

Seidel K, Beck J, Stieglitz L, Schucht P, Raabe A. The warning-sign hierarchy between quantitative subcortical motor mapping and continuous motor evoked potential monitoring during resection of supratentorial brain tumors. J Neurosurg. 2013;118(2):287–96.
24)

Seidel K, Beck J, Stieglitz L, Schucht P, Raabe A. Low Threshold Monopolar Motor Mapping for Resection of Primary Motor Cortex Tumors. Neurosurgery. 2012;71(1):104–14.
25)

Raabe A, Beck J, Schucht P, Seidel K. Continuous dynamic mapping of the corticospinal tract during surgery of motor eloquent brain tumors: evaluation of a new method. J Neurosurg. 2014;120(5)1015–24. doi: 10.3171/2014.1.JNS13909.
26)

Schucht P, Seidel K. Beck J, Murek M, Jilch A, Wiest R, et al. Intraoperative monopolar mapping during 5-ALA-guided resections of glioblastomas adjacent to motor eloquent areas: evaluation of resection rates and neurological outcome. Neurosurg Focus. 2014;27(6):E16.
28)

Gras-Combe G, Moritz-Gasser S, Herbet G, Duffau H. Intraoperative subcortical electrical mapping of optic radiations in awake surgery for glioma involving visual pathways. J Neurosurg. 2012;117(3):466–73.

Microvascular decompression for hemifacial spasm outcome

Microvascular decompression for hemifacial spasm outcome

Microvascular decompression is an effective treatment for hemifacial spasm. Given that postoperative delayed cure was unavoidable, even with accurate identification of the offending vessel and sufficient decompression of the root exit zone, the delayed cure should be considered in patients undergoing reoperation due to lack of remission or relapse after the operation. Additionally, the timing of efficacy assessments should be delayed 1).

The definitive treatment for hemifacial spasm is microvascular decompression (MVD), which cures the disease in 85% to 95% of patients according to reported series. In expert hands, the MVD procedure can be done with relatively low morbidity.

Post-operatively, there may be episodes of mild HFS, however they usually begin to diminish 2–3 days following MVD. Severe spasm that does not abate suggests failure to achieve adequate decompression, and reoperation should be considered.

Surgical results of MVD depends on the duration of symptoms (shorter duration has better prognosis) as well as on the age of the patient (elderly patients do less well). Complete resolution of HFS occurred in 44 (81%) of 54 patients undergoing MVD, however, 6 of these patients had relapse 2). 5 patients (9%) had partial improvement, and 5 (9%) had no relief.


Complete resolution of spasm occurs in ≈ 85–93% 3) 4) 5) 6) 7). Spasm is diminished in 9%, and unchanged in 6% 8). Of 29 patients with complete relief, 25 (86%) had immediate post-op resolution, and the remaining 4 patients took from 3 mos to 3 yrs to attain quiescence.

Recurrence

References

1)

Li MW, Jiang XF, Wu M, He F, Niu C. Clinical Research on Delayed Cure after Microvascular Decompression for Hemifacial Spasm. J Neurol Surg A Cent Eur Neurosurg. 2019 Oct 10. doi: 10.1055/s-0039-1698461. [Epub ahead of print] PubMed PMID: 31600810.
2)

Auger RG, Peipgras DG, Laws ER. Hemifacial Spasm: Results of Microvascular Decompression of the Facial Nerve in 54 Patients. Mayo Clin Proc. 1986; 61:640–644
3)

Rhoton AL. Comment on Payner T D and Tew J M: Recurren ce of Hemifacial Spasm After Microvascular Decompression. Neurosurgery. 1996; 38
4)

Jannetta PJ. Neurovascular Compression in Cranial Nerve and Systemic Disease. Ann Surg. 1980; 192:518–525
5)

Loeser JD, Chen J. Hemifacial Spasm: Treatment by Microsurgical Facial Nerve Decompression. Neurosurgery. 1983; 13:141–146
6)

Huang CI, Chen IH, Lee LS. Microvascular Decompression for Hemifacial Spasm: Analyses of Operative Findings and Results in 310 Patients. Neurosurgery. 1992; 30:53–57
7) , 8)

Payner TD, Tew JM. Recurrence of Hemifacial Spasm After Microvascular Decompression. Neurosurgery. 1996; 38:686–691
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