**Question:** In one of the following conditions cavities filled with fluid is seen in the centre of spinal cord:

A. Spinal cord injury
B. Syringomyelia
C. Syringohydromyelia
D. Tuberculous meningitis

**Core Concept:**

The central cavities filled with fluid in the spinal cord are known as syrinxes or syrinx cavities. These can be observed in various neurological conditions affecting the spinal cord. Syrinxes are usually secondary to a primary spinal cord pathology, such as:

**Why the Correct Answer is Right:**

C. Syringohydromyelia (SHM) is the correct answer because it refers to an enlarged central canal filled with cerebrospinal fluid (CSF) in the spinal cord, resulting from a disruption of the blood-spinal cord barrier due to a congenital or acquired cause. In this condition, the spinal cord fluid space enlarges, leading to cavitation.

**Why Each Wrong Option is Incorrect:**

A. Spinal cord injury (SCI) typically results in contusions, hematomas, or transections, rather than cavitation.

B. Syringomyelia (SM) refers to the formation of a cavitary lesion in the spinal cord secondary to a communication between the subarachnoid space and the central canal, typically caused by a spinal cord injury. Although cavitation may occur, the primary focus of SM is on the formation of the cavitary lesion and not the presence of a cavitary lesion due to a spinal cord injury.

D. Tuberculous meningitis (TM) is an infection of the meninges, causing inflammation and secondary damage to the spinal cord. While spinal cord involvement may occur, TM primarily affects the meninges and brain, not specifically the cavitation of the spinal cord.

**Clinical Pearl:**

Syringohydromyelia is characterized by the combination of cavitation and dilation of the central canal due to a disruption in the blood-spinal cord barrier. This condition is often associated with congenital or acquired causes, such as trauma, infections, or tumors. The presence of cavitation in the spinal cord can be indicative of underlying pathology and serves as a critical clinical clue for further investigation and diagnosis.

**Correct Answer Explanation:**

Cavitary changes in the spinal cord are primarily seen in syringomyelia (SM), which is caused by the formation of a cavitary lesion within the spinal cord due to a communication between the subarachnoid space and the central canal. This communication allows the cerebrospinal fluid (CSF) to flow into the spinal cord, leading to cavitation and dilation of the central canal.

**Why Syringomyelia is the Right Answer:**

Syringomyelia is the correct answer because it is characterized by the combination of cavitation and dilation of the central canal due to disruption in the blood-spinal cord barrier. This condition can be associated with congenital or acquired causes, such as trauma, infections, or tumors. The presence of cavitation in the spinal cord can serve as a critical clinical clue for further investigation and diagnosis.