Delayed Cerebral abscess following a retained shrapnel

Abstract

Retained foreign bodies following penetrating brain injuries continue to pose therapeutic dilemmas. Previously used aggressive approach involving extensive wound debridement and removal of foreign bodies caused additional neurological deficit with higher mortality. Less aggressive approach used more recently involving decompressive craniectomy has lead to higher incidence of retained foreign bodies with potential of infective sequelae. We describe one such case where, in presence of a retained foreign body, an intracranial abscess formed after a gap of 17 yrs. The case has peculiar radiological and morphological findings.

Introduction

Penetrating Brain Injuries (PBI) are accompanied by sense of despair and doom. Most of the mortality and morbidity is because of the primary injury but delayed complications are common. Philosophy of its management has undergone a paradigm shift from an aggressive approach of wound debridement, exploration of splinter track and removal of foreign bodies during WW1 and Korean wars to a more conservative approach of local debridements, decompressive craniectomies with duraplasty and leaving the inaccessible retained foreign bodies behind. The newer approach although beneficial has lead to certain peculiar and previously unknown complications. We describe one such rare complication wherein the patient developed a cerebral abscess after a period of 17 years in the vicinity of retained metal splinter. The case is peculiar not only because of delayed presentation but also because of its radiological peculiarities and therapeutic challenges.

Case report

A 51 years old male patient sustained a splinter injury brain following a grenade blast in 2001. Entry wound was in left supra-orbital area and splinter traversed the left hemicerebrum to lodge in (Lt) parieto-occipital area just 1 cm from the bone (Fig. 1). Frontal sinus was not breeched. He was conscious at the time of presentation and was managed by local debridement, antibiotics and anti-epileptics.

Fig. 1.

Radiological visualisation of foreign body. (a): Radiography Skull Lat View showing foreign body. (b): X-Ray Skull AP View showing foreign body. (c): Lat view in 3D Reconstruction of skull showing foreign body. (d): AP view in 3D reconstruction of skull showing entry wound.

He was administered Amoxycillin pluys Clavulanic acid, Amikacin and Metronidazole injections in antimeningitic doses. However the duration of administration of antibiotics could not be ascertained from old documents. Patient had an uneventful recovery and was kept under regular follow-up. He remained asymptomatic till June 2017 when he had Generalised Tonic Clonic Seizures (GTCS) and developed persistent headache and weakness of left upper and lower limb. CECT brain revealed conglomerate ring enhancing lesions (REL) around the retained splinter with significant cerebral edema. Patient was afebrile, with no leucocytosis and had conglomerate RELs on CECT brain. CSF biochemistry revealed moderately low sugar with raised proteins commensurate with tuberculosis. Tubercular granuloma was suspected and anti-tubercular therapy (ATT) was started. Patient showed clinical improvement with resolution of headache and improvement in hemiparesis. Complete radiological resolution of the abscess occurred over 3 months. ATT was continued for 18 months. Patient remained asymptomatic for 12 months after completion of ATT till Jan 2020 when he again developed right hemiparesis and global headache which was moderate in intensity without any diurnal variation. A CECT Brain revealed multiple ring enhancing lesions with significant cerebral edema.

Clinically patient was conscious but confused and had dysarthria. He was afebrile and had contralateral hemiparesis with Grade 4/5 power. He was radiologically evaluated with an NCCT and CECT Brain. Retained splinter was present just under the parietal bone. Multiple conglomerate ring enhancing lesions in left Parieto-occipital region with significant cerebral edema were present (Fig. 3). He was not found to have any septic foci or deranged blood sugar. His blood cultures were sterile and he had no immunocompromising conditions. His echocardiography was also normal. Patient consent for inclusion in study was also obtained.

Fig. 3.

Radiological appearance of abscess. (a): CECT brain at Initial presentation as conglomerate lesions. (b): CECT brain at the time of second presentation showing abscess with edema and mass effect. (c): Axial view after surgery. (d) Coronal View after surgery.

Surgery

A left parieto occipital free flap craniotomy was done. Dura was found adhered to the underlying arachnoid and had to be separated with sharp dissection. Arachnoid was thickened, yellowish and had lost its transparency. Intra-operatively a large abscess cavity with shrapnel as one of its walls was identified (Fig. 2). The wall was thick and fibrotic and contained whitish thin pus inside. There were multiple thin walled abscesses adjacent to this. A trans-sulcal approach was taken to the retained foreign body and dissection was done in the surrounding gliotic area keeping very close to the abscess wall. There was a thick yellowish-white free flowing liquid in all the abscess cavities.

Fig. 2.

Intra-operative appearance (a): Gliotic area just over the abscess (b): Early view of the abscess and foreign body as its wall. (c): Shrapnel after removal. (d): Multiple abscesses removed.

Gram Staining, ZN Staining, Fungal staining were negative from the evacuated pus. Aerobic, Anaerobic and Fungal Cultures were also negative. Gene Expert for tuberculosis was Negative. Histo-pathological examination of the abscess wall revealed foreign body giant cells and was suggestive of pyogenic abscess.

Patient had an uneventful recovery and his clouded consciousness improved. Injectable antibiotic therapy was given for 6 weeks followed by two weeks of oral antibiotics. Although controversial but in view of significant edema causing contralateral hemiparesis, altered mentation and dysarthria, steroids were administered and rapidly tapered over 2 weeks.

Discussion

Penetrating Brain Injury (PBI) poses significant threat to life. Infectious complications like local wound infection, meningitis, ventriculitis and cerebral abscesses are significant contributors to the mortality and morbidity of PBIs. Better and timely use of optimal antibiotics have caused reduction of infections. Military injuries (4–11%) as compared to civilian injuries (1–5%) have higher infectious components.¹ Presence of contaminants like skin, hair, bone pieces and foreign objects in the wounds predispose them to infectious.¹ Retained bone fragments predispose the patient to 10 times higher incidence of abscess formation.²

Following an analysis of PBI of Vietnam war it was suggested that all effort should be taken to debride the missile track and as far as possible all foreign objects along this track should be aggressively removed so as to reduce the infectious complications. Principles of management however have undergone a paradigm change with newer lessons learnt and currently consensus is on aggressive decompression of the brain. Aggressive debridement and attempts at removal of foreign bodies located at depth are not encouraged.³

In the present case the splinter injury was managed only by local debridement of the entry wound at left supra-orbital region. The splinter had travelled across left hemicerebrum and was lodged just under the ipsilateral parietal bone and no attempt could be made to debride the whole track and remove the foreign body. Patient remained asymptomatic for 17 years and thereafter developed cerebral abscess. Cerebral abscesses following PBI generally occur within 4–6 weeks.² Delayed occurrence of cerebral abscesses have been reported upto 7 years after the initial injury but only a few cases beyond this period. The incidence is higher in cases with retained bone pieces and less so with retained metal fragments, revitalized brain and in driven debris.⁴ The metallic splinter as well as the debris clinging to it tends to be sterile because of the high temperatures. Moreover the cavity behind the splinter tends to get sealed off.²

In the present case CECT brain revealed multiple conglomerate lesions with enhancement of the meninges in the vicinity of splinter. Cerebral abscesses whether pyogenic, tubercular or fungal are difficult to differentiate in-spite of their peculiar radiological features.⁵ Conglomerate lesions are commonly associated with neuro-tuberculosis^4,6 but occasionally have also been reported with Nocardiosis, Blastomycosis and Neurocysticercosis.7, 8, 9 Other CT features considered predictive of a tuberculoma include peripheral enhancement of a mass larger than 20 mm¹⁰ with an isodense center; moderate to severe perilesional edema; and a mass with lobulated margins and multiple masses. Another common presentation is a confluence of rings and discs resulting in a lobulated mass.^11,12 To our knowledge the only time a conglomerate lesion has been described following a PBI was by Lee et al⁵ in the year 2000 in a patient who was injured 47 years ago and unlike the present case the shrapnel and the lesion in their case was just under the entry wound. The present case is peculiar not only because of the radiological appearance suggestive of tubercular granuloma but also because the foreign body was lodged far away from the entry wound. Inspite of the bullet traversing whole of hemi-cerebrum antero-posteriorly, it became the focus of infection leading to abscess formation.

The micro-organisms at the site of injury usually succumb to the antibiotics and immune response mounted by the host. However in presence of foreign bodies the dormant micro-organisms with decreased virulence have the potential for delayed activation. Exact reason why it occurs is a matter of speculation but is definitely a result of an interplay of host's immunity and microbial virulence.⁵ Wannamaker evaluated the neurosurgical infections sustained in Korean battle and found gram positive cocci and gram negative bacilli like pseudomonas to be the causative organisms.¹³ Pseudomonas,⁵ Clostridium bifermentans¹⁴ have also been reported to cause delayed abscesses following PBI. Hagan et al² analysed the infections occurring in the early post-injury period after Vietnamese war and isolated Staphylococcus epidermis, Bacillus species, Klebsiella species, Pseudomonas aeruginosa, Aerobacter aerogenes, Serratia marcescens, Enterococci, Paecilomyces species, Pseudomonas aeruginosa, Corynebacterium species and Candida albicans.

The present case responded well to anti-tubercular therapy and the abscesses completely resolved within 3 months of starting ATT. Rifampicin as a part of Anti-tubercular therapy has the potential to be effective in certain other infections. In addition to mycobacterium its spectrum includes gram-positive cocci (except for some enterococci), H. influenzae, N. gonorrhoeae, N. meningitidis, Legionella, and L. monocytogenes.¹⁵ Possibly it was this action of Rifampicin which led to clinical and radiological improvement of the patient. In case of infection in the presence of a foreign body, this was likely suboptimal and lead to recurrence of the abscess after 1 year and had to be operated for a cure. We failed to isolate an organisms by conventional microbiological methods and the likely cause is administration of antibiotics before surgery. Another cause could be presence of an organism which has fastidious culture requirements not met in the culture medias used. A more aggressive approach to isolate the organism by molecular detection methods like qPCR and Next Generation Sequencing, although not resorted to in the present case is strongly recommended¹⁶

Conclusion

Delayed abscess following retained foreign bodies are rare but can still occur and radiologically they may be conglomerate ring enhancing lesions. Removal of the foreign body is a prerequisite for complete cure in addition to a suitable antibiotic administered for an optimal period.

Disclosure of competing interest

The authors have none to declare.