Quantitative Study of Posterior Fossa Crowdedness in Hemifacial Spasm.
OBJECTIVE
To quantitatively study the degree of posterior fossa crowdedness (PFC) in patients with hemifacial spasm (HFS) and to further investigate whether overcrowding in posterior fossa affects the efficacy and safety of microvascular decompression.


METHODS
We conducted a prospective case-control study of patients diagnosed with HFS and sex- and age-matched healthy control patients. All subjects underwent high-resolution, 3-dimensional magnetic resonance imaging, and posterior fossa crowdedness index (PFCI) and cerebrospinal fluid volume (CSFV) were measured. Patients with HFS underwent primary microvascular decompression and long-term follow-up. Associations of PFCI and other factors with operative outcomes and complications were analyzed.


RESULTS
The study enrolled 153 subjects: 102 patients and 51 control subjects. Compared with control subjects, patients had a more PFC (PFCI: 83.2% vs. 80.2%; P = 0.005) and smaller posterior fossa CSFV (16,248.0 mm(3) vs. 20,054.0 mm(3); P = 0.001). The mean effective space of posterior fossa cerebrospinal fluid in patients with HFS was 11.8% smaller than in control subjects (P = 0.004). Compared with men, women showed larger PFCI (83.6% vs. 82.2%; P = 0.012) and smaller PF CSFV (16,027.5 mm(3) vs. 17,299.5 mm(3); P = 0.009). Sixty-one patients (59.8%) were spasm-free immediately postoperatively, and 95 (93.1%) were spasm-free at follow-up. Complication rates were 9.8% in the short term, and 2.9% at follow-up. Lower PFCI (odds ratio [OR] 0.63; P = 0.019) and severe indention (OR 1.41; P = 0.027) were significantly associated with better short-term outcomes. Greater PFCI (OR 2.05, P = 0.008) was associated with greater early complication incidence.


CONCLUSIONS
Patients with HFS had more PFC. PFC potentially leads to cranial nerve and vascular structure crowding, which may increase HFS risk. PFC was significantly associated with poor short-term outcomes and greater incidence of early complications but not long-term outcomes and complications.
Department of Neurosurgery, West China Hospital, Sichuan University, Chengdu, China.
Jian
J
Cheng
Department of Neurosurgery, West China Hospital, Sichuan University, Chengdu, China.
Yuan
Y
Fang
Department of Neurosurgery, West China Hospital, Sichuan University, Chengdu, China. Electronic address: zhangheng.cn@gmail.com.
Heng
H
Zhang
Department of Neurosurgery, West China Hospital, Sichuan University, Chengdu, China.
Ding
D
Lei
Department of Radiology, West China Hospital, Sichuan University, Chengdu, China.
Wentao
W
Wu
Department of Neurosurgery, West China Hospital, Sichuan University, Chengdu, China.
Chao
C
You
Department of Neurosurgery, West China Hospital, Sichuan University, Chengdu, China.
Boyong
B
Mao
Department of Neurosurgery, West China Hospital, Sichuan University, Chengdu, China.
Ke
K
Mao
D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D003388:Cranial Fossa, Posterior / Q000473:pathology* / Q000601:surgery*; D005260:Female; D005500:Follow-Up Studies; D019569:Hemifacial Spasm / Q000134:cerebrospinal fluid / Q000473:pathology* / Q000601:surgery*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D061145:Microvascular Decompression Surgery / Q000009:adverse effects / Q000379:methods*; D008875:Middle Aged; D019635:Neurosurgical Procedures / Q000379:methods; D011183:Postoperative Complications / Q000453:epidemiology; D011446:Prospective Studies; D012737:Sex Factors; D016896:Treatment Outcome; D055815:Young Adult
Hemifacial spasm; Microvascular decompression; Neurovascular conflict; Pathogenesis; Posterior fossa crowdedness; Prognosis