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Explain

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This image is a study note (from "eBTR by Dr. Zainab Vora") on the complications of mastoiditis / CSOM (Chronic Suppurative Otitis Media). Here's a full breakdown of every concept shown:

Mastoiditis - Clinical Overview

The top-left image shows mastoiditis with two stages noted:

1st: Ironed-out mastoiditis - the normal bony septa of the mastoid air cells are destroyed, giving a homogeneous cloudy appearance on imaging.
Reservoir sign - pus accumulates in a "reservoir," meaning the mastoid is filled with pus and bulging.

Soft Tissue Abscesses - By Site

When mastoid infection erodes through the cortex, pus tracks into soft tissue. The abscess is named by where it drains:

Abscess Name	Site of Pus Collection
Retro-auricular (MC)	Most common - behind the auricle (subperiosteal abscess)
Bezold abscess	Pus breaks through the mastoid tip, tracks into the SCM (sternocleidomastoid) muscle
Citelli's abscess	Pus tracks into the digastric muscle (posterior belly) - also called CD (Citelli/Digastric)
Luc's abscess	Pus bursts through the outer cortex into the EAC (External Auditory Canal)

K J Lee's Essential Otolaryngology: "Bezold abscess is abscess in the sternocleidomastoid muscle secondary to perforation of the tip of the mastoid by infection."

Imaging - CT Head

The two CT scans shown demonstrate:

NCCT (Non-Contrast CT) - shows a hyperdense lesion, consistent with fresh thrombus (clot) in the lateral/transverse sinus (labeled "TS" = Transverse Sinus, with temporal bone circled).
CECT (Contrast-Enhanced CT) - shows a filling defect - the thrombus doesn't enhance because it lacks blood flow. This is the classic "empty delta sign" appearance.

The bottom-left image labeled CSOM shows a clinical photo of discharge/pus in the ear.

Lateral Sinus Thrombosis (Transverse/Sigmoid Sinus)

This is a serious intracranial complication of mastoiditis. Key signs and tests:

Sign/Test	Explanation
Griesinger sign	Edema and tenderness over the mastoid cortex caused by thrombosis of the mastoid emissary vein as a result of lateral (transverse) sinus thrombosis
Tobey-Ayer test	Compress the IJV (Internal Jugular Vein) on the affected side - CSF pressure does NOT rise (blocked sinus). Compressing the opposite IJV causes a normal CSF pressure rise.
Crowe-Beck test	Compress both IJVs - no rise in CSF pressure when affected side is compressed (same principle as Tobey-Ayer)
Picket fence fever	Characteristic spiking, intermittent fever pattern in septic lateral sinus thrombosis - looks like a picket fence on a fever chart

K J Lee's Essential Otolaryngology: "Griesinger sign: edema and tenderness over the mastoid cortex associated with thrombosis of the mastoid emissary vein as a result of lateral sinus thrombosis."

Gradenigo Syndrome (Apical Petrositis)

This is a triad caused when infection from the mastoid extends into the petrous apex of the temporal bone, irritating nearby structures:

Triad:

Ear discharge (otorrhoea from CSOM)
Diplopia (double vision) - due to CN VI (Abducens nerve) palsy, as it passes through Dorello's canal at the petrous apex
Retro-orbital pain - due to irritation of CN V (Trigeminal nerve) - specifically the ophthalmic division (V1)

K J Lee's Essential Otolaryngology: "Gradenigo syndrome: otorrhoea, retro-orbital pain, and lateral rectus palsy secondary to irritation of CN VI within Dorello canal... Due to infection extending from middle ear and mastoid air cells into the pneumatized petrous apex."

Summary Concept Map

CSOM / Mastoiditis
        |
        ├── Soft tissue abscess (retro-auricular > Bezold > Citelli > Luc's)
        |
        ├── Lateral sinus thrombosis
        |       ├── Griesinger sign (emissary vein edema)
        |       ├── Tobey-Ayer test (no CSF pressure rise on compression)
        |       ├── Crowe-Beck test
        |       └── Picket fence fever (septic emboli)
        |
        └── Apical petrositis → Gradenigo Syndrome
                ├── Ear discharge (CN = CSOM itself)
                ├── CN VI palsy (diplopia)
                └── CN V irritation (retro-orbital pain)

The CT imaging correlation is key for exams: NCCT shows hyperdense clot, CECT shows a filling defect in the sinus - both point to lateral sinus thrombosis, a life-threatening complication requiring urgent mastoidectomy plus anticoagulation.

Hyperdense means

On a non-contrast CT (NCCT), density refers to how bright or dark a structure appears, measured in Hounsfield Units (HU).

Hyperdense = Brighter White on CT

Term	Appearance	HU Range	Examples
Hyperdense	Bright white	Higher HU	Fresh blood, clot, calcium, bone
Isodense	Same as brain	~30-40 HU	Subacute blood, normal brain
Hypodense	Dark/black	Lower HU	Water, edema, CSF, air, fat

Why is Fresh Blood/Clot Hyperdense?

Fresh thrombus (clot) is hyperdense because:

Hemoglobin (globin protein) in clotted blood has high X-ray attenuation
The clot is denser than surrounding brain tissue
It absorbs more X-rays, so it appears bright white on NCCT

HU of fresh clot = ~56-90 HU vs. normal brain = ~30-40 HU

In the Context of Lateral Sinus Thrombosis

NCCT - the transverse/sigmoid sinus appears hyperdense (bright white) because it contains a fresh clot instead of flowing blood
CECT - contrast fills the patent (open) parts of the sinus but cannot fill the clot - so the clot appears as a dark filling defect surrounded by enhancing sinus wall - this is the classic "empty delta sign"

Simple Memory Rule

"More dense material = more X-ray absorption = whiter on CT"

Bone (most white) > Fresh blood/clot > Brain > Water > Fat > Air (most black)

So when you see "hyperdense sinus" on NCCT - think clot inside the sinus, which in the setting of mastoiditis = lateral sinus thrombosis.

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