| Risk Factors | Frequency | Percent % |
| Otitis Media | 6 | 11.1% |
| Mastoiditis | 2 | 3.7% |
| Head Trauma | 2 | 3.7% |
| Neurosurgical Procedure | 7 | 13.0% |
| Pulmonary Infection | 1 | 1.9% |
| Cardiac Disease | 8 | 14.8% |
| Other | 7 | 13.0% |
| No Risk Factor | 21 | 38.9% |
| Total | 54 | 100.0% |