Subarachnoid Pleural Fistula Due to Gunshot Wound.

Subarachnoid pleural fistula (SPF) is an extremely rare complication that occurs after dural space and vertebral columns injuries. SPF is divided into two diagnoses based on the absence or presence of pneumocephalus and pneumorrachis. While pneumocephalus is defined as the presence of air the cranial cavity, if there is air in the spinal canal, this is defined as pneumorrhachis. In general, the association of SPF with pneumocephalus and pneumorrachis is rare but can occur after blunt trauma. In our patient, pneumorrhachis and pneumocephalus with SBF developed after the patient suffered a gunshot wound. This paper reports an SPF case accompanied by pneumorrachis and pneumocephalus, which occurred after thoracic spine injury due to a gunshot wound.

Introduction

Subarachnoid pleural fistula (SPF) is an extremely rare complication that occurs after injury of dural space and vertebral columns. In SPF, both pneumocephalus and pneumorrachis may be seen. Pneumocephalus is defined as the presence of air in cranial cavity and is most commonly caused by trauma. It has been reported that the incidence of the pneumocephalus due to trauma is 5.6%. A rare condition in which air enters the spinal canal after trauma is called pneumorrachis. Occurence of pneumorrhachis is frequently asymptomatic and does not require any specific treatment because air is reabsorbed spontaneously without leaving any neurological sequelae. This paper reports an SPF case accompanied by pneumorrachis and pneumocephalus, which occurred after thoracic spine injury due to a gunshot wound.

Case Report

A 20-year-old male patient with a gunshot wound was brought to the emergency room by air ambulance. His medical history was normal. In the emergency department, he had a poor general condition: he was unconscious, non-oriented, and non-cooperative. Glasgow Coma Scale was evaluated as E1M5Vt. The patient was brought in intubated with bilateral chest tube. His blood pressure was 86/43 mmHg, cardiac pulse 86 beat/min, respiration rate 24 breaths/min, axilla temperature 36.7 °C, and oxygen saturation 96%.

While examining the patient's head and neck, it was observed that there was a laceration on the right parietal and frontal area and also a subcutaneous emphysema spanning from the right side of neck to inguinal region. In respiratory system examination, the bullet entry hole on the posterior region of left shoulder and bullet exit hole on anterior of right shoulder were detected. Examination of other systems yielded normal findings.

Computed tomography (CT) of the brain and maxillofacial area exhibited bilateral putamen, cerebellar haemorrhage, and pneumocephalus without any bone fracture (Figure 1). In CT of cervical vertebrae and thorax, a fracture in T2 vertebra along with pneumorrachis, haemopneumothorax, and pneumomediastinium were detected (Figure 2a, b). In other tomographic examinations no acute pathologies were observed. The pateint was transferred to ICU after consultation with anesthesia and reanimation clinics. The pateint died on the seventh day in anesthesia ICU.

Figure 1

Bilateral pneumocephalus in brain CT.

Figure 2

The fracture of T2 vertebra with pneumorrachis (a), haemopneumothorax and pneumomediastinium (b).

Discussion

SPF can be caused by blunt or penetrating trauma. The main cause of blunt and penetrating traumas are motor vehicle accidents and gunshot injuries. SPF is divided into two groups: the first group consists of absence of radiological pneumorrhachis and pneumocephalus, and the second group is defined as the presence of pneumocephalus and pneumorrachis. The second group is rare and the most common feature of this group is its secondary occurence after blunt trauma. However, in this case, pneumorrhachis and pneumocephalus developed after a gunshot wound not due to a blunt trauma. Pneumocephalus and pneumorrachis are important radiological findings that may indicate serious pathologies.

Pneumocephalus develops after a trauma if there is a dural membrane tear, leading to contact with air and greater air pressure in this area compared to the cerebrospinal fluid (CSF) pressure. This is rare if no tension pneumothorax is present as the pressure of pleural space is under atmospheric pressure. In this case, the patient did not have tension pneumothorax. For this reason, it is thought that high air pressure may also cause secondary pneumocephalus and SPF without tension pneumothorax.

Pressure can change depending on the patient's position. Intratechal pressure at thoracic vertebra level injuries is probably low in supine position and under the state of shock. In addition, CSF production decreases about 30% after stimulation of the sympathetic nervous system. In this case, a decrease in CSF production resulting in decrease in CSF pressure can lead to formation of SPF easily as observed in our patient. Wide dural defect due to gunshot wound can lead to the loss of a large amount CSF, a condition that causes CSF pressure to be reduced to zero. In addition, high intrathoracic pressure caused by gunshot shock wave may be higher than that of cerebrospinal fluid pressure. In our case, it is thought that the pateint developed pneumocephalus and SPF due to pressure changes at high altitudes during patient transfer to ER by air ambulance.

There is no definitive method in the treatment of SPF. Vertebral column injury, dural and pleural tears are all developed after high-energy trauma mechanisms. This may explain why this condition results in high mortality rates.

Conclusion

SPF is a rare complication that occurs following an injury to the vertebral column and is usually reported after a blunt trauma. Here we are reporting a case of a victim with pneumorrhachis and pneumocephalus after a gunshot wound, leading to SPF as a secondary defect after trauma. Airborne transfer of patients with vertebral injuries may lead to SPF due to air pressure changes at high elevations; thus caution must be exercised for the air ambulance transfer of such patients.

Conflict of Interest

The authors declare that there is no potential conflicts of interest.