Table 2.

Studies included in the present review.

Study, Year	Study Design	Participants				Control Group (N)	Blood Coagulation Disorders	Results
		N	Diagnosis	Age (Mean ± SD)	% Male
Capaccio et al., 2007 [11]	Prospective cohort study	100	SSNHL	48.12 ± 14.6	56	200 healthy subjects	Factor V Leiden G1691A mutation; prothrombin G20210A mutation	Factor V Leiden G1691A and prothrombin G20210A mutations were found to be more frequent in patients with SSNHL than in controls (p = 0.001). A significantly major frequency of multiple allelic mutations was found in SSNHL patients compared to controls (p = 0.0001).
Görür et al., 2005 [12]	Cohort study	56	SSNHL	42.6 ± 18.2 (10–87 range)	48.2	95 healthy subjects	Factor V Leiden G1691A mutation; prothrombin G20210A mutation	Factor V Leiden mutation was found to be more frequent in patients with SSNHL than in controls (p = 0.02). No significant difference was found between the groups in regard to prothrombin G20210A mutation (p = 0.58). Factor V Leiden and prothrombin mutations were heterozygous in all subjects.
Cadoni et al., 2006 [13]	Prospective cohort study	48	SSNHL	♂ 46 (21–74 range); ♀ 50 (22–75 range)	41.7	48 healthy subjects	Factor V Leiden G1691A mutation; prothrombin G20210A mutation; APCR; protein S deficiency; protein C deficiency; antithrombin III deficiency	No significant association was found between SSNHL and factor V G1691A mutation or prothrombin G20210A mutation or APCR or abnormal levels of protein S, protein C, and antithrombin III.
Mercier et al., 1999 [14]	Retrospective case–control study	368	Deep-vein thrombosis	41 (17–72 range)	27.4	395 non-thrombotic subjects	Factor V Leiden G1691A mutation; prothrombin G20210A mutation; protein S deficiency; protein C deficiency; antithrombin III deficiency	Prothrombin G20210A mutation was found to be an independent risk factor for unilateral SSNHL (p < 0.0001). No significant association was found between SSNHL and factor V Leiden G1691A mutation or abnormal levels of protein S, protein C, and antithrombin III.
Lovato et al., 2004 [15]	Case report	1	Unilateral SSNHL	41	0	N/A	Factor V Leiden G1691A mutation	Unilateral SSNHL onset with a pure-tone average (average of the pure-tone thresholds at 0.5, 1, 2, and 4 kHz) of 33.8 dB in a woman presenting a factor V heterozygous state. Intravenous betamethasone disodium phosphate 4 mg and 250 mL of saline solution with mannitol 10% daily were administered over 11 days. A deep-vein thrombosis in the lower extremity and pulmonary embolism were subsequently diagnosed and an oral anticoagulant therapy was prescribed. The 2-month follow-up pure-tone audiometry showed complete hearing recovery.
Crassard et al., 1997 [16]	Case report	1	Unilateral SSNHL	48	0	N/A	Factor V Leiden G1691A mutation; APCR	Unilateral moderate SSNHL onset presenting with cerebral sinus venous thrombosis in a woman with factor V heterozygous state and increased APCR. After intravenous heparin therapy then switched to oral anticoagulants, complete hearing loss recovery was reported in 6 months (audiometric data not shown).
Gattringer et al., 2012 [17]	Case report	1	Unilateral SSNHL	42	0	N/A	Factor V Leiden G1691A mutation	Unilateral moderate SSNHL onset presenting with cerebral sinus venous thrombosis in a woman with a factor V heterozygous state. After intravenous heparin therapy then switched to oral anticoagulants, complete hearing loss recovery was reported (audiometric data not shown).
Patscheke et al., 2001 [18]	Case–control study	118	SSNHL	45.5	57.6	352 healthy subjects	Prothrombin G20210A mutation	In a group of patients in which the first episode of SSNHL occurred before the age of 40, a statistically significant major frequency of prothrombin G20210A mutation was observed compared to control subjects and a 16-fold increased risk for SSNHL in carriers of the mutation was found (OR = 16, 95% CI 1.95 to 202; p = 0.0091).
Park et al., 2001 [19]	Case report	1	Bilateral SSNHL	34	0	N/A	Protein S deficiency	Sequential bilateral pantonal profound SSNHL onset in a woman with protein S deficiency. The patient also presented a small atrial septal defect and multiple acute cerebellar and cerebral microinfarcts. Rivaroxaban was administered (5 mg per day) together with 1 g per day of intravenous methylprednisolone. Partial hearing loss recovery was observed, during the audiological follow-up.
Zajtchuk et al., 1979 [20]	Case–control study	14	SSNHL	N/A	N/A	50 healthy subjects	Antithrombin III deficiency; factor VIII	Abnormal values of antithrombin III and factor VIII were reported in 4 and 1 patients, respectively. No statistical analysis was performed due to the small sample.
Gold et al., 1993 [21]	Case report	1	Bilateral SSNHL	48	0	N/A	Antithrombin III deficiency	Sequential bilateral SSNHL onset in a woman with antithrombin III deficiency; no hearing threshold improvement was observed after the corticosteroid therapy.
Kashiwazaki et al., 2012 [22]	Case report	1	Unilateral conductive hearing loss	46	100	N/A	Haemophilia A	Unilateral conductive hearing loss onset in a man due to the presence of temporal bone haemophilic pseudotumor inducing stenosis of the auditory external canal. An improvement in the hearing threshold was reported after removal of the pseudotumor by petrosectomy.
Schlegelberger et al., 1986 [23]	Case report	1	Hearing loss	22	0	N/A	Thrombasthenia	Presence of hearing loss, triphalangia of thumbs, and Glanzmann’s thrombasthenia, suggesting a probable autosomal recessive syndrome. Information about the onset and the features of the hearing loss was not reported.
Fisgin et al., 2009 [24]	Case report	1	Bilateral hearing loss	5	100	N/A	ITP	Bilateral hearing loss onset in a boy with acute ITP purpura. A bilateral spontaneous hemotympanum was diagnosed. No hearing test was reported.

Abbreviation: SSNHL, sudden sensorineural hearing loss; APCR, activated protein C resistance; N/A, not available; ITP, immune thrombocytopenia.