Intracranial Complications of Otitis Media

A. Extradural Abscess

Definition: Collection of pus between bone and dura.

Pathology

• Acute OM: Bone destroyed by hyperaemic decalcification.
• Chronic OM: Bone destroyed by cholesteatoma (pus in direct contact with dura).
• Venous Thrombophlebitis: Bone over dura remains intact.
• Sites: Middle/Posterior cranial fossa or Perisinus (outside lateral venous sinus).
• Appearance: Dura may look healthy or discoloured with granulations.

Clinical Features

Suspect if:

• Persistent headache on the side of otitis media.
• Severe ear pain.
• General malaise + low-grade fever.
• Pulsatile purulent ear discharge.
• Spontaneous Drainage Sign: Headache disappears when pus flows freely from ear.

Treatment

1. Surgery (Cortical/Modified Radical/Radical Mastoidectomy):
   • Remove overlying bone until healthy dura is reached.
   • If tegmen/sinus plate is intact but abscess is suspected: Deliberately remove bone to evacuate pus.
2. Antibiotics: Minimum 5 days. Monitor for sinus thrombosis/meningitis.

B. Subdural Abscess

Definition: Pus between dura and arachnoid.

Pathology

• Spread: Direct erosion of bone/dura OR Thrombophlebitis (bone intact).
• Pus spreads rapidly in subdural space (pressure on cerebral hemisphere). May become loculated.

Clinical Features (Triad of Causes)

1. Meningeal Irritation	2. Cortical Thrombophlebitis	3. Raised ICP
- Headache - Fever (102°F+) - Neck Rigidity - (+) Kernig's Sign	- Aphasia, Hemiplegia - Hemianopia - Jacksonian Epilepsy (focal fits) - Status epilepticus	- Papilloedema - Ptosis - Dilated pupil (CN III) - Drowsiness

Treatment

• Neurological Emergency: Series of Burr holes or Craniotomy to drain empyema.
• Antibiotics: Intravenous.
• Ear Surgery: Mastoidectomy done after infection is controlled.

C. Meningitis

Definition: Inflammation of leptomeninges (pia & arachnoid). Most common intracranial complication.

Etiology

• Infants/Children: Follows Acute OM (Blood-borne).
• Adults: Follows Chronic OM (Bone erosion or retrograde thrombophlebitis).

Clinical Features

• High fever (102-104°F) with chills.
• Headache, Photophobia, Irritability.
• Neck Rigidity.
• (+) Kernig’s Sign: Extension of leg with thigh flexed causes pain.
• (+) Brudzinski’s Sign: Flexion of neck causes flexion of hip/knee.
• Reflexes: Exaggerated initially → Sluggish/Absent later.

Diagnosis (CSF Findings)

Parameter	Meningitis Finding
Appearance	Turbid
Cells	Raised (up to 1000/mL, Polymorphs)
Protein	Raised
Sugar & Chlorides	Reduced / Diminished

Treatment

1. Medical (Priority over surgery):

• IV Antimicrobials (Aerobic + Anaerobic cover).
• Corticosteroids (reduce neuro/audio complications).

2. Surgical:

• Acute OM: Myringotomy or Cortical Mastoidectomy.
• Chronic OM: Radical/Modified Radical Mastoidectomy.
• Timing: Once patient is stable, or urgently if no response to meds.

D. Otogenic Brain Abscess

Frequency: Cerebral (Temporal lobe) 2x more common than Cerebellar.

Bacteriology

• Aerobic: Staph, Strep pneumo/haemolyticus, Proteus, E. Coli, Pseudomonas.
• Anaerobic: Peptostreptococcus, Bacteroides fragilis.

Pathology: 4 Stages

Clinical Features

A. General (Raised ICP)

• Headache (Worse in morning).
• Vomiting (Projectile, common in cerebellar).
• Papilloedema (Late in cerebral, Early in cerebellar).
• Slow pulse & Subnormal temperature.

B. Localizing Features (Comparison)

Temporal Lobe Abscess	Cerebellar Abscess
Nominal Aphasia: Can't name objects (if dominant hemisphere).	Headache: Suboccipital area.
Homonymous Hemianopia: Visual field loss opposite to lesion.	Nystagmus: Spontaneous, irregular, towards lesion side.
Motor Paralysis: Contralateral face/arm/leg.	Ataxia: Ipsilateral, staggers to lesion side.
Epileptic Fits: Uncinate gyrus (Taste/smell hallucinations).	Dysdiadochokinesia: Slow/irregular rapid movements.
Pupil: Oculomotor palsy (Transtentorial herniation).	Intention Tremor & Past Pointing.

Treatment

1. Medical:
   • High dose IV antibiotics (Chloramphenicol + 3rd Gen Cephalosporins).
   • Metronidazole for anaerobes (B. fragilis).
   • Aminoglycosides (Gentamicin) for Pseudomonas.
   • Decrease ICP: Dexamethasone (4mg IV 6hrly) or Mannitol 20% (0.5g/kg).
2. Neurosurgical: Aspiration (via burr hole), Excision, or Incision/Drainage. (Repeat CT to check size).
3. Otologic: Radical Mastoidectomy after abscess is controlled.

E. Lateral Sinus Thrombophlebitis

(Syn: Sigmoid Sinus Thrombosis)

Pathology Steps

1. Perisinus Abscess: Abscess outside dural wall.
2. Endophlebitis: Fibrin/platelets deposit on inner wall (Mural Thrombus).
3. Occlusion: Lumen obliterated, intrasinus abscess forms.
4. Extension:
   • Proximal: To Sup. Sagittal/Cavernous sinus.
   • Distal: To Mastoid emissary, Jugular bulb/vein.

Clinical Features

• Fever: Hectic Picket-Fence type with chills/rigors (Septicaemia). Profuse sweating follows.
• Griesinger’s Sign: Oedema over posterior mastoid (Emissary vein thrombosis).
• Tobey-Ayer Test: Compress vein on thrombosed side → NO rise in CSF pressure.
• Crowe-Beck Test: Pressure on healthy jugular → Retinal/Supraorbital vein engorgement.
• Papilloedema: If Right sinus (larger) or Sagittal sinus involved.
• Jugular Tenderness: If thrombus extends to neck (Torticollis may be present).

Investigations

• Blood Smear: Rule out Malaria.
• Blood Culture: Take during chill.
• Imaging: CT shows "Delta Sign" (Empty triangle with rim enhancement). MR Venography is best.

Treatment

1. IV Antibiotics: Continue for 1 week post-op.
2. Surgery (Mastoidectomy):
   • Expose sinus dura, drain perisinus abscess.
   • If intrasinus abscess/clot: Pack sinus above and below (between bone and dura).
   • Incise dura, remove infected clot.
   • Leave healthy red clot alone. Remove pack after 5-6 days.
3. Ligation of IJV: Rarely done (if emboli continue despite treatment).
4. Anticoagulants: Only if spreading to cavernous sinus.

F. Otitic Hydrocephalus

Key Concept: Raised ICP + Normal CSF Chemistry.

• Mechanism: Sinus thrombosis extends to Sup. Sagittal Sinus → Arachnoid villi cannot absorb CSF.
• Features: Severe headache, Diplopia (CN VI), Papilloedema (5-6 diopters).
• CSF: Pressure >300 mm H2O. Sterile. Normal sugar/protein.
• Treatment: Acetazolamide, Steroids, Lumboperitoneal shunt (to prevent optic atrophy/blindness).