**Question:** Astacia-Abasia seen in

A. Motor neuron disease
B. Sensory neuron disease
C. Sensory neuron disease
D. Motor and sensory neuron disease

**Correct Answer:** B. Sensory neuron disease

**Core Concept:** Astasia-abasia refers to a clinical syndrome characterized by uncoordinated movement and intention tremors. It is caused by a dysfunction in the sensory neurons, which are responsible for transmitting sensory information from the periphery to the brain.

**Why the Correct Answer is Right:** Sensory neuron diseases cause a disruption in the transmission of sensory information, leading to impaired perception of body position and movement. This results in difficulties with motor control and intention tremors, which are the defining features of astasia-abasia.

**Why Each Wrong Option is Incorrect:**

A. Motor neuron disease (e.g., amyotrophic lateral sclerosis) primarily affects motor neurons, leading to muscle weakness and atrophy, but not typically causing uncoordinated movement and intention tremors.

B. Motor neuron disease (e.g., motor neuron disease) affects both motor and sensory neurons, but the correct answer is sensory neuron disease because motor neuron diseases do not primarily cause the specific clinical signs of astasia-abasia.

C. Sensory neuron disease affects sensory neurons solely, leading to impaired sensation and sensation-related motor control, but not causing uncoordinated movement and intention tremors.

D. Motor and sensory neuron disease affects both motor and sensory neurons, but the correct answer is sensory neuron disease because motor neuron diseases do not primarily cause the specific clinical signs of astasia-abasia.

**Sensory neuron disease:** This option is correct because it involves the impairment of sensory neurons, leading to the clinical features of astasia-abasia, such as uncoordinated movement and intention tremors. These symptoms result from the disruption of sensory feedback, which is essential for maintaining posture, balance, and motor control.

**Clinical Pearl:** Astasia-abasia is a rare condition, and its presentation can be helpful in narrowing down the differential diagnosis for uncoordinated gait and intention tremors.

**Why it matters:** Understanding the underlying pathology, whether it involves motor, sensory, or both neurons, is crucial for accurate diagnosis and appropriate management of patients presenting with uncoordinated movement and intention tremors.